Semiconductor device and method of driving the semiconductor device

ABSTRACT

Display irregularities in light emitting devices, which develop due to dispersions per pixel in the threshold value of TFTs for supplying electric current to light emitting elements, are obstacles to increasing the image quality of the light emitting devices. An electric potential in which the threshold voltage of a TFT ( 105 ) is either added to or subtracted from the electric potential of a reset signal line ( 110 ) is stored in capacitor means ( 108 ). A voltage, in which the corresponding threshold voltage is added to an image signal, is applied to a gate electrode of a TFT ( 106 ). TFTs within a pixel are disposed adjacently, and dispersion in the characteristics of the TFTs does not easily develop. The threshold value of the TFT ( 105 ) is thus cancelled, even if the threshold values of the TFTs ( 106 ) differ per pixel, and a predetermined drain current can be supplied to an EL element ( 109 ).

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device having atransistor and a method of driving the semiconductor device. Further,the present invention relates to an active matrix light emitting devicehaving a semiconductor device with a thin film transistor (hereinafterreferred to as a TFT) formed on an insulator such as glass or plastic,and a method of driving the semiconductor device. Also, the presentinvention relates to electronic equipment using this type of lightemitting device.

[0003] 2. Description of the Related Art

[0004] The development of display devices in which light emittingelements such as electro luminescence (EL) elements are used, has becomeactive in recent years. Being self-luminous, the light emitting elementis high in visibility and eliminates the need for a backlight that isnecessary in liquid crystal display devices (LCDs) etc., thereby beingcapable of reducing the thickness of such devices. Also, the lightemitting devices may have virtually no limit in terms of viewing angles.

[0005] The term EL element indicates an element having a light emittinglayer in which luminescence generated by application of an electricfield can be obtained. There are light emission when returning to a basestate from a singlet excitation state (fluorescence), and light emissionwhen returning to a base state from a triplet excitation state(phosphorescence) in the light emitting layer. A light emitting deviceof the present invention may use either of the aforementioned types oflight emission.

[0006] EL elements normally have a laminate structure in which a lightemitting layer is sandwiched between a pair of electrodes (anode andcathode). A laminate structure consisting of an anode, a holetransporting layer, a light emitting layer, an electron transportinglayer, and a cathode can be given as a typical structure. Further,structures having the following layers laminated in order between ananode and a cathode also exist: a hole injecting layer, a holetransporting layer, a light emitting layer, and an electron transportinglayer; and a hole injecting layer, a hole transporting layer, a lightemitting layer, an electron transporting layer, and an electroninjecting layer. Any of the above-stated structures may be employed asthe EL element structure used in the light emitting device of thepresent invention. Furthermore, fluorescent pigments and the like mayalso be doped into the light emitting layer.

[0007] Here, all layers formed in EL elements between the anode and thecathode are referred to generically as “EL layers”. The aforementionedhole injecting layer, hole transporting layer, light emitting layer,electron transporting layer, and electron injecting layer are allincluded in the category of EL layers, and light emitting elementsstructured by an anode, an EL layer, and a cathode are referred to as ELelements.

[0008] The structure of a pixel in a general light emitting device isshown in FIG. 8. Note that an EL display device is used as an example ofa typical light emitting device. The pixel shown in FIG. 8 has a sourcesignal line 801, a gate signal line 802, a switching TFT 803, a driverTFT 804, capacitor means 805, an EL element 806, an electric currentsupply line 807, and an electric power source line 808.

[0009] The connectivity relationship between each portion is explained.The term TFT as used here refers to a three terminal element having agate, a source, and a drain, but it is difficult to make cleardistinctions between the source and the drain due to the structure ofTFTs. One terminal, the source or the drain, is therefore denoted as afirst electrode, and the other terminal is denoted as a second electrodewhen explaining the connections between the elements. The terms sourceand drain are used in the case where a definition of the electricpotential of each element is necessary relating to on and off states ofthe TFT (for example, when explaining a voltage between the gate and thesource of the TFT).

[0010] Further, the TFT being in an on state refers to a state in whichthe voltage between the gate and the source of the TFT exceeds thethreshold value of the TFT, and electric current flows between thesource and the drain. The TFT being in an off state refers to a state inwhich the voltage between the gate and the source of the TFT is lessthan the threshold value of the TFT, and the electric current does notflow between the source and the drain. Note that there are cases inwhich a slight amount of the electric current, referred to as a leakcurrent, flows between the source and the drain even if the voltagebetween the gate and the source of the TFT is less than the thresholdvalue. However, this state is treated similarly to the off state.

[0011] A gate electrode of the switching TFT 803 is connected to thegate signal line 802, a first electrode of the switching TFT 803 isconnected to the source signal line 801, and a second electrode of theswitching TFT 803 is connected to a gate electrode of the driver TFT804. A first electrode of the driver TFT 804 is connected to theelectric current supply line 807, and a second electrode of the driverTFT 804 is connected to a first electrode of the EL element 806. Asecond electrode of the EL element 806 is connected to the electricpower source line 808. There is a mutual electric potential differencebetween the electric current supply line 807 and the electric powersource line 808. Further, the capacitor means 805 may be formed betweenthe gate electrode of the driver TFT 804 and the line having a fixedelectric potential, such as the electric current supply line 807, inorder to maintain the voltage between the gate and the source of thedriver TFT 804 during light emission.

[0012] An image signal input to the source signal line 801 is then inputto the gate electrode of the driver TFT 804 if a pulse is input to thegate signal line 802 and the switching TFT 803 is on. The voltagebetween the gate and the source of the driver TFT 804, and the amount ofthe electric current flowing between the source and the drain of thedriver TFT 804 (hereinafter referred to as a drain current), aredetermined in accordance with the electric potential of the input imagesignal. This electric current is supplied to the EL element 806, and theEL element 806 emits light.

[0013] TFTs formed by polycrystalline silicon (hereinafter referred toas P—Si) have a higher field-effect mobility than TFTs formed by usingamorphous silicon (hereinafter referred to as A-Si), and a larger oncurrent, and therefore are very suitable as transistors used in lightemitting devices.

[0014] Conversely, TFTs formed by P—Si have a problem in that dispersionin their electrical characteristics tends to develop due to defects incrystal grain boundaries.

[0015] If there is a dispersion in TFT threshold values, for example adispersion per pixel in the threshold values of the driver TFTs 804 inFIG. 8, then a difference in the brightness of the EL elements 806develops due to dispersion in the value of the drain current of theTFTs, corresponding to the dispersion in the TFT threshold values, evenif the same image signal is input to different pixels. This particularlybecomes a problem for display devices employing an analog gray scalemethod.

[0016] It has been proposed recently that these types of TFT thresholdvalue dispersions can be corrected. A structure shown in FIG. 10 can begiven as one example of such as proposal (refer to patent document 1).

[0017] [Patent Document 1] International Publication Number 99-48403Pamphlet (p. 25, FIG. 3, FIG. 4).

[0018] A pixel shown in FIG. 10A has a source signal line 1001, first tothird gate signal lines 1002 to 1004, TFTs 1005 to 1008, capacitor means1009 (C₂) and 1010 (C₁), an EL element 1011, an electric current supplyline 1012, and an electric power source line 1013.

[0019] A gate electrode of the TFT 1005 is connected to the first gatesignal line 1002, a first electrode of the TFT 1005 is connected to thesource signal line 1001, and a second electrode of the TFT 1005 isconnected to a first electrode of the capacitor means 1009. A second toelectrode of the capacitor means 1009 is connected to a first electrodeof the capacitor means 1010, and a second electrode of the capacitormeans 1010 is connected to the electric current supply line 1012. A gateelectrode of the TFT 1006 is connected to the second electrode of thecapacitor means 1009 and the first electrode of the capacitor means1010, a first electrode of the TFT 1006 is connected to the electriccurrent supply line 1012, and a second electrode of the TFT 1006 isconnected to a first electrode of the TFT 1007 and a first electrode ofthe TFT 1008. A gate electrode of the TFT 1007 is connected to thesecond gate signal line 1003, and a second electrode of the TFT 1007 isconnected to the second electrode of the capacitor means 1009. A gateelectrode of the TFT 1008 is connected to the third gate signal line1004, and a second electrode of the TFT 1008 is connected to a firstelectrode of the EL element 1011. A second electrode of the EL element1011 is connected to the electric power source line 1013, and has amutual electric potential difference with the electric current supplyline 1012.

[0020] Operation is explained using FIGS. 10A and 10B, and FIGS. 11A to11F. FIG. 10B shows image signals input to the source signal line 1001and the first to the third gate signal lines 1002 to 1004, and showspulse timing. FIG. 10B is divided into sections I to VIII correspondingto each operation shown in FIGS. 11A to 11F. Further, a structure usingfour TFTs is used as an example in the pixel shown in FIGS. 10A and 10B,with all four being p-type TFTs. The TFTs therefore turn on when an Llevel signal is input to their gate electrodes, and turn off when an Hlevel signal is input. Furthermore, although image signals input to thesource signal line 1001 are shown here which have a pulse shape in orderto indicate input periods only, predetermined analog electric potentialsmay also be used for an analog gray scale method.

[0021] First, L level is input to the first and the third gate signallines 1002 and 1004, and the to TFTs 1005 and 1008 turn on (section I).The second gate signal line 1003 then becomes L level, and the TFT 1007turns on. Electric charge accumulates in the capacitor means 1009 and1010 as shown in FIG. 11A. The TFT 1006 turns on at the point when anelectric potential difference between both electrodes of the capacitormeans 1010, in other words, when a voltage maintained in the capacitormeans 1010, exceeds a threshold value |V_(th)| of the TFT 1006 (sectionII).

[0022] The third gate signal line 1004 then becomes H level, and the TFT1008 turns off. The electric charge which has accumulated in thecapacitor means 1009 and 1010 thus moves once again, and the voltagestored in the capacitor means 1010 soon becomes equal to |V_(th)|. Theelectric potential of the electric current supply line 1012 and theelectric potential of the source signal line 1001 are both an electricpotential V_(DD) at this point, as shown in FIG. 11B, and therefore thevoltage maintained in the capacitor means 1009 also becomes equal to|V_(th)|. The TFT 1006 therefore soon turns off.

[0023] The second gate signal line 1003 becomes H level after thevoltages maintained in the capacitor means 1009 and 1010 become equal to|V_(th)|, as discussed above, and the TFT 1007 turns off (section IV).|V_(th)| is thus stored in the capacitor means 1009 by this operation,as shown in FIG. 11C.

[0024] A relationship like that of Eq. (1) results for an electriccharge Q₁ stored at this point in the capacitor means 1010 (C₁).Similarly, a relationship like that of Eq. (2) results for an electriccharge Q₂ stored at this point in the capacitor means 1009 (C₂).

[0025] [Eq. (1)]

[0026] [Eq. (2)]

[0027] Input of an image signal is then performed as shown in FIG. 11D(section V). The image signal is output to the source signal line 1001,and the electric potential of the source signal line 1001 changes fromthe electric potential V_(DD) to an electric potential V_(Data) of theimage signal (the TFT 1006 is a p-channel TFT here, and thereforeV_(DD)>V_(Data)). If the electric potential of the gate electrode of theTFT 1006 is taken as an electric potential V_(P), and the electriccharge in the node is taken as Q, then relationships like those of Eq.(3) and Eq. (4) develop due to conservation law of charge including thecapacitor means 1009 and 1010.

[0028] [Eq. (3)]

[0029] [Eq. (4)]

[0030] From Eqs. (1) to (4), the electric potential V_(P) of the gateelectrode of the TFT 1006 can be expressed by Eq. (5).

[0031] [Eq. (5)]

[0032] A voltage V_(GS) between the gate and the source of the TFT 1006is therefore expressed by Eq. (6).

[0033] [Eq. (6)]

[0034] The term V_(th) is contained in the right-hand side of Eq. (6).That is, the threshold voltage of the TFT 1006 in each pixel is added tothe image signal input from the source signal line 1001, and this isstored by the capacitor means 1009 and 1010.

[0035] The first gate signal line 1002 becomes H level when the input ofthe image signal is complete, and the TFT 1005 turns off (section VI). The source signal line 1001 then returns to a predetermined electricpotential (section VII). Operations for writing in the image signal tothe pixels are thus complete (FIG. 11E).

[0036] The third gate signal line 1004 then becomes L level, the TFT1008 turns on, and the EL element 1011 emits light due to electriccurrent flowing in the EL element 1011, as shown in FIG. 11F. The amountof electric current flowing in the EL element 1011 at this point dependsupon the voltage between the gate and the source of the TFT 1006, and adrain current IDS flowing in the TFT 1006 is expressed by Eq. (7).

[0037] [Eq. (7)]

[0038] It can be seen from Eq. (7) that the drain current IDS of the TFT1006 does not depend on the threshold value V_(th). The value of theelectric current flowing in the EL elements 1011 of each of the pixelstherefore does not change, even if there is dispersion in the thresholdvalues of the TFTs 1006 in each of the pixels. Electric currenttherefore flows correctly in the EL elements 1011 in accordance with theimage signal V_(Data).

[0039] However, the drain current IDS in Eq. (7) does depend upon thecapacitances C₁ and C₂ with the aforementioned structure. That is, thedrain current IDS will have dispersion if the capacitance values of thecapacitor means 1009 and 1010 have dispersion.

SUMMARY OF THE INVENTION

[0040] An object of the present invention is therefore to provide asemiconductor device capable of correcting dispersions in TFT thresholdvalues due to the aforementioned problem, specifically a semiconductordevice having a structure that is not influenced by dispersions incapacitance values. In addition, an object of the present invention isto provide a method of driving the semiconductor device.

[0041] Operating principles of the present invention are explained usingFIGS. 14A to 14E. Consider circuits like those of FIG. 14A or 14B.Switching elements 1403 and 1413 are elements that are controlled byinput signals, and may be elements capable of being placed in aconductive or a non-conductive state. For example, elements such asTFTs, with which on and off can be selected by an input signal, may beemployed.

[0042] Further, an element in which electric current develops only in asingle direction when an electric potential difference is imparted toboth electrodes of the element is defined as a rectifying element.Diodes and TFTs having a short circuit between their gate and drain(this state is denoted as a diode connection) can be given as examplesof rectifying elements.

[0043] Consider circuits in which the switching elements 1403 and 1413,capacitor means 1402 and 1412, and rectifying elements 1401 and 1411 areconnected as shown in FIGS. 14A and 14B. The rectifying element 1401uses a p-channel TFT, and the rectifying element 1411 uses an n-channelTFT.

[0044] Terminals in each circuit are denoted by α, β, γ, and δ. Fixedelectric potentials are imparted to each of the terminals α to γ. Theelectric potential imparted to the terminals α and β in FIG. 14A istaken as V_(SS), and the electric potential imparted to the terminal γis taken as V_(Reset) (V_(Reset)≧V_(SS)+|V_(th)P|, where V_(th)P is thethreshold value of the rectifying element 1401). The electric potentialimparted to the terminals α and β for the case of FIG. 14B is taken asV_(x), and the electric potential imparted to the terminal y is taken asV_(Reset) (V_(Reset)≦V_(x)−|V_(th)N|, where V_(th)N is the thresholdvalue of the rectifying element 1411).

[0045] The switching elements 1403 and 1413 are conductive during aperiod denoted by symbol i in FIG. 14C. In FIG. 14A, the electricpotential of a gate electrode and a drain electrode of the TFT 1401,which is a rectifying element, drops to become V_(SS) in FIG. 14A. Onthe other hand, in FIG. 14B, the electric potential of a gate electrodeand a drain electrode of the TFT 1411, which is a rectifying element,increases to become V_(x). The voltage between the source and the drainof both the TFT 1401 and the TFT 1411 is higher than the absolute valueof the threshold voltage, and therefore both turn on.

[0046] The switching elements 1403 and 1413 then become non-conductiveduring a period denoted by symbol ii in FIG. 14C. The TFTs 1401 and 1411are both on at this point, and electric current develops in each betweentheir source and drain. The electric potential of the gate electrode andthe drain electrode of the TFT 1401 increases in FIG. 14A, and theelectric potential of the gate electrode and the drain electrode of theTFT 1411 drops in FIG. 14B. The voltage between the source and the drainof the TFT 1401 and the voltage between the source and the drain of theTFT 1411, in other words the voltages between the gate and the source ofthe TFTs 1401 and 1411, therefore become smaller.

[0047] The voltages between the gate and the source of the TFTs 1401 and1411 each therefore become equal to the threshold value of theirrespective TFTs. The TFTs 1401 and 1411 therefore turn off. The electricpotential differences between the electric potential of the drainelectrode of the TFTs 1401 and 1411, and the terminal α are stored bythe capacitor means 1402 and 1412 at this point.

[0048] V_(Reset)−|V_(th)P| is therefore output from the terminal δ inFIG. 14A during a period denoted by symbol iii in FIG. 14C, andV_(Reset)+|V_(th)N| is output from the terminal δ in FIG. 14B.

[0049] It can be seen that the threshold voltage of the TFTs 1401 and1411 can be output for both FIG. 14A and FIG. 14B. For example, if asignal is input to the terminal α in this state, then capacitivecoupling occurs by the capacitor means 1402 and 1412, and the electricpotential of the terminal δ changes by the amount of the voltage of theinput signal. The TFT threshold voltage already appears at the terminalδ, and therefore there is a correction applied with respect to thesignal input by the amount of the TFT threshold voltage.

[0050] A different structure having the same operating principle mayalso be used as shown in FIGS. 14D and 14E, in which a diode 1410 orcapacitor means 1420 is formed as a substitute for the switching element1403, and the electric potential of the gate electrode and the drainelectrode of the TFT 1401 is lowered by reducing the electric potentialof the terminal β (V_(SS) here). The electric potential of the terminalδ at this point can drop to V_(SS)+|V_(th)D|, where V_(th)D is thethreshold value of the diode 1410). Electric current does not flow inthe reverse direction in the case of FIG. 14D provided that the electricpotential of the terminal β is increased (V_(DD) here) after theelectric potential of the gate electrode and the drain electrode of theTFT 1401 are initially reduced, and this therefore becomes similar tomaking a switching element non-conductive.

[0051] Note that although the TFT 1401 uses a p-channel TFT here, it mayalso use an n-channel TFT. In this case, the drain electrode and thegate electrode of the TFT 1401 are connected to the terminal γ side.Similarly, although the TFT 1411 uses an n-channel TFT, it may also usea p-channel TFT. The drain electrode and the gate electrode of the TFT1411 are then connected to the terminal γ side for this case.

[0052] Further, the TFTs 1401 and 1411 may also use diodes. For thediodes to be used here, in addition to diodes having a normal p-njunction, TFTs having the aforementioned diode connection may also beused.

[0053] Correcting dispersion in TFT threshold values in a light emittingdevice, and reducing dispersion in the brightness of EL elements aretaken as objectives here and methods for accomplishing the objectivesare explained. The operating principle of the present invention is notlimited to the correction of dispersion in TFT threshold values,however, and of course it is also possible to apply the presentinvention to other electronic circuits.

[0054] Structures of the present invention are discussed below.

[0055] According to the present invention, there is provided asemiconductor device comprising:

[0056] a rectifying element;

[0057] capacitor means; and

[0058] a switching element,

[0059]  characterized in that:

[0060] a first electrode of the rectifying element is electricallyconnected to a first electrode of the capacitor means and a firstelectrode of the switching element.

[0061] According to the present invention, there is provided asemiconductor device comprising:

[0062] a first rectifying element having a first electrode;

[0063] a second rectifying element having a first electrode; and

[0064] capacitor means,

[0065]  characterized in that:

[0066] a first electrode of the first rectifying element electricallyconnected to a first electrode of the capacitor means and a firstelectrode of the second rectifying element.

[0067] According to the present invention, there is provided asemiconductor device comprising:

[0068] a rectifying element;

[0069] capacitor means; and

[0070] a switching element,

[0071]  characterized in that:

[0072] an electric potential V₁ of a first electric power source isimparted to a first electrode of the rectifying element;

[0073] a second electrode of the rectifying element is electricallyconnected to a first electrode of the capacitor means and a firstelectrode of the switching element;

[0074] an electric potential V₂ of a second electric power source isimparted to a second electrode of the switching element;

[0075] a signal having an electric potential that is greater than orequal to an electric potential V₃ and less than or equal to (V₃+anelectric potential V_(Data)), or greater than or equal to (V₃−V_(Data))and less than or equal to V₃, is input to a second electrode of thecapacitor means; and

[0076] a signal having an electric potential equal to any one of(V₁+|V_(th)|), V₂, and (V₁+|V_(th)|±V_(Data)) is obtained from thesecond electrode of the rectifying element when a threshold voltage ofthe rectifying element is taken as V_(th).

[0077] According to the present invention, there is provided asemiconductor device comprising:

[0078] a rectifying element;

[0079] capacitor means; and

[0080] a switching element,

[0081]  characterized in that:

[0082] an electric potential V₁ of a first electric power source isimparted to a first electrode of the rectifying element;

[0083] a second electrode of the rectifying element is electricallyconnected to a first electrode of the capacitor means and a firstelectrode of the switching element;

[0084] an electric potential V₂ of a second electric power source isimparted to a second electrode of the switching element;

[0085] a signal having an electric potential that is greater than orequal to an electric potential V₃ and less than or equal to (V₃+anelectric potential V_(Data)), or greater than or equal to (V₃−V_(Data))and less than or equal to V₃, is input to a second electrode of thecapacitor means; and

[0086] a signal having an electric potential equal to any one of(V₁−|V_(th)|), V₂, and (V₁−|V_(th)|+V_(Data)) is obtained from thesecond electrode of the rectifying element when a threshold voltage ofthe rectifying element is taken as V_(th).

[0087] According to the present invention, there is provided asemiconductor device comprising:

[0088] a first rectifying element;

[0089] a second rectifying element; and

[0090] capacitor means,

[0091]  characterized in that:

[0092] an electric potential V₁ of a first electric power source isimparted to a first electrode of the first rectifying element;

[0093] a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element;

[0094] a first signal having an electric potential greater than or equalto an electric potential V₂ and less than or equal to an electricpotential V₂′ is input to a second electrode of the second rectifyingelement;

[0095] a second signal having an electric potential that is greater thanor equal to an electric potential V₃ and less than or equal to (V₃+anelectric potential V_(Data)), or greater than or equal to (V₃−V_(Data))and less than or equal to V₃, is input to a second electrode of thecapacitor means; and

[0096] a signal having an electric potential equal to any one of(V₁−|V_(th)|), (V₂+V_(th)2), and (V₁−|V_(th)|+V_(Data)) is obtained fromthe second electrode of the first rectifying element when a thresholdvoltage of the first rectifying element is taken as V_(th)1 and athreshold voltage of the second rectifying element is taken as V_(th)2.

[0097] According to the present invention, there is provided asemiconductor device comprising:

[0098] a first rectifying element;

[0099] a second rectifying element; and

[0100] capacitor means,

[0101]  characterized in that:

[0102] an electric potential V₁ of a first electric power source isimparted to the first electrode of the first rectifying element;

[0103] a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element;

[0104] a first signal having a voltage amplitude of an electricpotential greater than or equal to an electric potential V₂ and lessthan or equal to an electric potential V₂′ is input to a secondelectrode of the second rectifying element;

[0105] a second signal having an electric potential that is greater thanor equal to an electric potential V₃ and less than or equal to (V₃+anelectric potential V_(Data)), or greater than or equal to (V₃−V_(Data))and less than or equal to V₃, is input to a second electrode of thecapacitor means; and

[0106] a signal having an electric potential equal to any one of(V₁+V_(th)1), (V₂′−V_(th)2), and (V₁+V_(th)1±V_(Data)) is obtained fromthe second electrode of the first rectifying element when a thresholdvoltage of the first rectifying element is taken as V_(th)1 and athreshold voltage of the second rectifying element is taken as V_(th)2.

[0107] According to the present invention, there is provided asemiconductor device, characterized in that:

[0108] the rectifying element is formed by using a transistor having aconnection between its gate and its drain;

[0109] V₁<V₂ if the transistor having a connection between its gate andits drain is an n-channel transistor; and

[0110] V₁>V₂ if the transistor having a connection between its gate andits drain is a p-channel transistor.

[0111] According to the present invention, there is provided asemiconductor device, characterized in that:

[0112] the first rectifying element is formed by using a transistorhaving a connection between its gate and its drain;

[0113] V₁<V₂ if the transistor having a connection between its gate andits drain is an n-channel transistor; and

[0114] V₁I>V₂ if the transistor having a connection between its gate andits drain is a p-channel transistor.

[0115] According to the present invention, there is provided asemiconductor device, further comprising a transistor, characterized inthat a gate electrode of the transistor is electrically connected to thefirst electrode of the capacitor means.

[0116] According to the present invention, there is provided asemiconductor device comprising a plurality of pixels, each pixelincluding:

[0117] a source signal line;

[0118] a first gate signal line;

[0119] a second gate signal line;

[0120] a reset electric power source line;

[0121] an electric current supply line;

[0122] a first transistor;

[0123] a second transistor;

[0124] a third transistor;

[0125] a fourth transistor;

[0126] capacitor means; and

[0127] a light emitting element,

[0128]  characterized in that:

[0129] a gate electrode of the first transistor is electricallyconnected to the first gate signal line;

[0130] a first electrode of the first transistor is electricallyconnected to the source signal line;

[0131] a second electrode of the first transistor is electricallyconnected to a first electrode of the capacitor means;

[0132] a second electrode of the capacitor means is electricallyconnected to a gate electrode of the second transistor, a firstelectrode of the second transistor, and a gate electrode of the thirdtransistor;

[0133] a second electrode of the second transistor is electricallyconnected to the reset electric power source line;

[0134] a first electrode of the third transistor is electricallyconnected to the electric current supply line;

[0135] a second electrode of the third transistor is electricallyconnected to a first electrode of the light emitting element;

[0136] a gate electrode of the fourth transistor is electricallyconnected to the second gate signal line;

[0137] a first electrode of the fourth transistor is electricallyconnected to the source signal line or the second electrode of the firsttransistor; and

[0138] a second electrode of the fourth transistor is electricallyconnected to the gate electrode of the second transistor, the firstelectrode of the second transistor, and the gate electrode of the thirdtransistor.

[0139] According to the present invention, there is provided asemiconductor device comprising a plurality of pixels, each pixelincluding:

[0140] a source signal line;

[0141] a first gate signal line;

[0142] a second gate signal line;

[0143] a reset electric power source line;

[0144] an electric current supply line;

[0145] a first transistor;

[0146] a second transistor;

[0147] a third transistor;

[0148] capacitor means;

[0149] a diode; and

[0150] a light emitting element,

[0151]  characterized in that:

[0152] a gate electrode of the first transistor is electricallyconnected to the first gate signal line;

[0153] a first electrode of the first transistor is electricallyconnected to the source signal line;

[0154] a second electrode of the first transistor is electricallyconnected to a first electrode of the capacitor means;

[0155] a second electrode of the capacitor means is electricallyconnected to a gate electrode of the second transistor, a firstelectrode of the second transistor, and a gate electrode of the thirdtransistor;

[0156] a second electrode of the second transistor is electricallyconnected to the reset electric power source line;

[0157] a first electrode of the third transistor is electricallyconnected to the electric current supply line;

[0158] a second electrode of the third transistor is electricallyconnected to a first electrode of the light emitting element;

[0159] a first electrode of the diode is electrically connected to thegate electrode of the second transistor, the first electrode of thesecond transistor, and the gate electrode of the third transistor; and

[0160] a second electrode of the diode is electrically connected to thesecond gate signal line.

[0161] According to the present invention, there is provided asemiconductor device comprising a plurality of pixels, each pixelincluding:

[0162] a source signal line;

[0163] a first gate signal line;

[0164] a second gate signal line;

[0165] a reset electric power source line;

[0166] an electric current supply line;

[0167] a first transistor;

[0168] a second transistor;

[0169] a third transistor;

[0170] a first capacitor means;

[0171] a second capacitor means; and

[0172] a light emitting element,

[0173]  characterized in that:

[0174] a gate electrode of the first transistor is electricallyconnected to the first gate signal line;

[0175] a first electrode of the first transistor is electricallyconnected to the source signal line;

[0176] a second electrode of the first transistor is electricallyconnected to a first electrode of the first capacitor means;

[0177] a second electrode of the first capacitor means is electricallyconnected to a gate electrode of the second transistor, a firstelectrode of the second transistor, and a gate electrode of the thirdtransistor;

[0178] a second electrode of the second transistor is electricallyconnected to the reset electric power source line;

[0179] a first electrode of the third transistor is electricallyconnected to the electric current supply line;

[0180] a second electrode of the third transistor is electricallyconnected to a light emitting element;

[0181] a first electrode of the second capacitor means is electricallyconnected to the gate electrode of the second transistor, the firstelectrode of the second transistor, and the gate electrode of the thirdtransistor; and

[0182] a second electrode of the second capacitor means is electricallyconnected to the second gate signal line.

[0183] According to the present invention, there is provided asemiconductor device comprising a plurality of pixels, each pixelincluding:

[0184] a source signal line;

[0185] a first gate signal line;

[0186] a second gate signal line;

[0187] a third gate signal line;

[0188] a reset electric power source line;

[0189] an electric current supply line;

[0190] a first transistor;

[0191] a second transistor;

[0192] a third transistor;

[0193] a fourth transistor;

[0194] a fifth transistor;

[0195] a first capacitor means;

[0196] a second capacitor means; and

[0197] a light emitting element,

[0198]  characterized in that:

[0199] a gate electrode of the first transistor is electricallyconnected to the first gate signal line;

[0200] a first electrode of the first transistor is electricallyconnected to the source signal line;

[0201] a second electrode of the first transistor is electricallyconnected to a first electrode of the first capacitor means;

[0202] a second electrode of the first capacitor means is electricallyconnected to a gate electrode of the second transistor, a firstelectrode of the second transistor, and a gate electrode of the thirdtransistor;

[0203] a second electrode of the second transistor is electricallyconnected to the reset electric power source line;

[0204] a first electrode of the third transistor is electricallyconnected to the electric current supply line;

[0205] a second electrode of the third transistor is electricallyconnected to a light emitting elements;

[0206] a gate electrode of the fourth transistor is electricallyconnected to the second gate signal line;

[0207] a first electrode of the fourth transistor is electricallyconnected to the source signal line or the second electrode of the firsttransistor;

[0208] a second electrode of the fourth transistor is electricallyconnected to the gate electrode of the second transistor, the firstelectrode of the second transistor, and the gate electrode of the thirdtransistor;

[0209] a first electrode of the second capacitor means is electricallyconnected to the second electrode of the first transistor;

[0210] a second electrode of the second capacitor means is electricallyconnected to the second electrode of the third transistor;

[0211] a gate electrode of the fifth transistor is electricallyconnected to the third gate signal line;

[0212] a first electrode of the fifth transistor is electricallyconnected to the second electrode of the third transistor; and

[0213] a second electrode of the fifth transistor is connected to anelectric power source electric potential that is equal to or lower thanan electric potential of a second electrode of the light emittingelement.

[0214] According to the present invention, there is provided asemiconductor device, further comprising:

[0215] an erasure gate signal line; and

[0216] an erasure transistor,

[0217]  characterized in that:

[0218] a gate electrode of the erasure transistor is electricallyconnected to the erasure gate signal line;

[0219] a first electrode of the erasure transistor is electricallyconnected to the electric current supply line; and

[0220] the second electrode of the erasure transistor is electricallyconnected to the gate electrode of the third transistor.

[0221] According to the present invention, there is provided asemiconductor device, further comprising:

[0222] an erasure gate signal line; and

[0223] an erasure transistor,

[0224]  characterized in that:

[0225] a gate electrode of the erasure transistor is electricallyconnected to the erasure gate signal line;

[0226] a first electrode of the erasure transistor is electricallyconnected to the electric current supply line; and

[0227] a second electrode of the erasure transistor is electricallyconnected to the second electrode of the first transistor.

[0228] According to the present invention, there is provided asemiconductor device, further comprising:

[0229] an erasure gate signal line; and

[0230] an erasure transistor,

[0231]  characterized in that:

[0232] the erasure transistor is formed between the electric currentsupply line and the first electrode of the third transistor, or betweenthe second electrode of the third transistor and the first electrode ofthe light emitting element; and

[0233] a gate electrode of the erasure transistor is electricallyconnected to the erasure gate signal line.

[0234] According to the present invention, there is provided asemiconductor device, characterized in that the second transistor andthe third transistor have the same polarity.

[0235] According to the present invention, there is provided a method ofdriving a semiconductor device, the semiconductor device comprising:

[0236] a rectifying element;

[0237] capacitor means; and

[0238] a switching element,

[0239]  characterized in that:

[0240] an electric potential V₁ of a first electric power source isimparted to a first electrode of the rectifying element;

[0241] a second electrode of the rectifying element is electricallyconnected to a first electrode of the capacitor means and a firstelectrode of the switching element; and

[0242] an electric potential V₂ of a second electric power source isimparted to a second electrode of the switching element;

[0243] the method of driving the semiconductor device comprising:

[0244] when a threshold voltage of the rectifying element is taken asV_(th), a first step of making the switching element conductive andsetting the electric potential of a second electrode of the rectifyingelement to V₂; and

[0245] a second step of making the switching element non-conductive,making the voltage between both electrodes of the rectifying elementconverge to the threshold voltage V_(th), and setting the electricpotential of the second electrode of the rectifying element to(V₁+V_(th)).

[0246] According to the present invention, there is provided a method ofdriving a semiconductor device, the semiconductor device comprising:

[0247] a rectifying element;

[0248] capacitor means; and

[0249] a switching element,

[0250]  characterized in that:

[0251] an electric potential V_(I) of a first electric power source isimparted to a first electrode of the rectifying element;

[0252] a second electrode of the rectifying element is electricallyconnected to the first electrode of the capacitor means and a firstelectrode of the switching element;

[0253] an electric potential V₂ of a second electric power source isimparted to a second electrode of the switching element; and

[0254] a signal having an electric potential that is greater than orequal to an electric potential V₃ and less than or equal to (V₃+anelectric potential V_(Data)), or greater than or equal to (V₃−V_(Data))and less than or equal to V₃, is input to a second electrode of thecapacitor means;

[0255] the method of driving the semiconductor device comprising:

[0256] when a threshold voltage of the rectifying element is taken asV_(th),

[0257] a first step of making the switching element conductive andsetting the electric potential of a second electrode of the rectifyingelement to V₂;

[0258] a second step of making the switching element non-conductive,making the voltage between both electrodes of the rectifying elementconverge to the threshold voltage V_(th), and setting the electricpotential of the second electrode of the rectifying element to(V₁+V_(th)); and

[0259] a third step of changing the electric potential of the secondelectrode of the capacitor means by V_(Data), and setting the electricpotential of the second electrode of the rectifying element to(V₁+V_(th)±V_(Data)).

[0260] According to the present invention, there is provided a method ofdriving a semiconductor device, the semiconductor device comprising:

[0261] a rectifying element;

[0262] capacitor means; and

[0263] a switching element,

[0264]  characterized in that:

[0265] an electric potential V₁ of a first electric power source isimparted to a first electrode of the rectifying element;

[0266] a second electrode of the rectifying element is electricallyconnected to a first electrode of the capacitor means and a firstelectrode of the switching element; and

[0267] an electric potential V₂ of a second electric power source isimparted to a second electrode of the switching element;

[0268] the method of driving the semiconductor device comprising:

[0269] when a threshold voltage of the rectifying element is taken asV_(th),

[0270] a first step of making the switching element conductive andsetting the electric potential of the second electrode of the rectifyingelement to V₂; and

[0271] a second step of making the switching element non-conductive,making the voltage between both electrodes of the rectifying elementconverge to the threshold voltage V_(th), and setting the electricpotential of the second electrode of the rectifying element to(V₁−|V_(th)|).

[0272] According to the present invention, there is provided a method ofdriving a semiconductor device, the semiconductor device comprising:

[0273] a rectifying element;

[0274] capacitor means; and

[0275] a switching element,

[0276]  characterized in that:

[0277] an electric potential V₁ of a first electric power source isimparted to a first electrode of the rectifying element;

[0278] a second electrode of the rectifying element is electricallyconnected to a first electrode of the capacitor means and a firstelectrode of the switching element;

[0279] an electric potential V₂ of a second electric power source isimparted to a second electrode of the switching element; and

[0280] a signal having an electric potential that is greater than orequal to an electric potential V₃ and less than or equal to (V₃+anelectric potential V_(Data)), or greater than or equal to (V₃−V_(Data))and less than or equal to V₃, is input to a second electrode of thecapacitor means;

[0281] the method of driving the semiconductor device comprising:

[0282] when a threshold voltage of the rectifying element is taken asV_(th),

[0283] a first step of making the switching element conductive andsetting the electric potential of the second electrode of the rectifyingelement to V₂;

[0284] a second step of making the switching element non-conductive,making the voltage between both electrodes of the rectifying elementconverge to the threshold voltage V_(th), and setting the electricpotential of the second electrode of the rectifying element to(V₁−|V_(th)|); and

[0285] a third step of changing the electric potential of the secondelectrode of the capacitor means by V_(Data), and setting the electricpotential of the second electrode of the rectifying element to(V₁−|V_(th)±V_(Data)).

[0286] According to the present invention, there is provided a method ofdriving a semiconductor device, characterized in that:

[0287] the semiconductor device further comprises a transistor; and

[0288] a gate electrode of the transistor is electrically connected tothe second electrode of the rectifying element.

[0289] According to the present invention, there is provided a method ofdriving a semiconductor device, the semiconductor device comprising:

[0290] a first rectifying element having a first electrode and a secondelectrode;

[0291] a second rectifying element having a first electrode and a secondelectrode; and

[0292] capacitor means,

[0293]  characterized in that:

[0294] an electric potential V₁ of a first electric power source isimparted to a first electrode of the first rectifying element;

[0295] a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element; and

[0296] a first signal having an electric potential greater than or equalto an electric potential V₂ and less than or equal to an electricpotential V₂′ is input to a second electrode of the second rectifyingelement;

[0297] the method of driving the semiconductor device comprising:

[0298] when a threshold voltage of the first rectifying element is takenas V_(th)1 and a threshold voltage of the second rectifying element istaken as V_(th)2,

[0299] a first step of setting the electric potential of a secondelectrode of the second capacitor means to V₂, and setting the electricpotential of the second electrode of the first rectifying element to(V₂+V_(th)2); and

[0300] a second step of setting the electric potential of a secondelectrode of the second capacitor means to V₂′, making the voltagebetween both electrodes of the first rectifying element converge to thethreshold voltage V_(th)1, and setting the electric potential of thesecond electrode of the first rectifying element to (V₁−|V_(th) 1|).

[0301] According to the present invention, there is provided a method ofdriving a semiconductor device, the semiconductor device comprising:

[0302] a first rectifying element;

[0303] a second rectifying element; and

[0304] capacitor means,

[0305]  characterized in that:

[0306] an electric potential V₁ of a first electric power source isimparted to a first electrode of the first rectifying element;

[0307] a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element;

[0308] a first signal having an electric potential greater than or equalto an electric potential V₂ and less than or equal to an electricpotential V₂′ is input to a second electrode of the second rectifyingelement; and

[0309] a second signal having an electric potential that is greater thanor equal to an electric potential V₃ and less than or equal to (V₃+anelectric potential V_(Data)), or greater than or equal to (V₃−V_(Data))and less than or equal to V₃, is input to a second electrode of thecapacitor means;

[0310] the method of driving the semiconductor device comprising:

[0311] when a threshold voltage of the first rectifying element is takenas V_(th)1 and a threshold voltage of the second rectifying element istaken as V_(th)2,

[0312] a first step of setting the electric potential of the secondelectrode of the second capacitor means to V₂, and setting the electricpotential of the second electrode of the first rectifying element to(V₂+V_(th)2);

[0313] a second step of setting the electric potential of a secondelectrode of the second capacitor means to V₂′, making the voltagebetween both electrodes of the first rectifying element converge to thethreshold voltage V_(th)1, and setting the electric potential of thesecond electrode of the first rectifying element to (V₁−|V_(th)1|); and

[0314] a third step of changing the electric potential of the secondelectrode of the capacitor means by V_(Data), and setting the electricpotential of the second electrode of the first rectifying element to(V₁−|V_(th)1|+V_(Data)).

[0315] According to the present invention, there is provided a method ofdriving a semiconductor device, the semiconductor device comprising:

[0316] a first rectifying element;

[0317] a second rectifying element; and

[0318] capacitor means;

[0319]  characterized in that:

[0320] an electric potential V₁ of a first electric power source isimparted to the first electrode of the first rectifying element;

[0321] a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element; and

[0322] a first signal having an electric potential greater than or equalto an electric potential V₂ and less than or equal to an electricpotential V₂′ is input to a the second electrode of the secondrectifying element;

[0323] the method of driving the semiconductor device comprising:

[0324] when a threshold voltage of the first rectifying element is takenas V_(th)1 and a threshold voltage of the second rectifying element istaken as V_(th)2,

[0325] a first step of setting the electric potential of a secondelectrode of the second capacitor means to V₂,′ and setting the electricpotential of the second electrode of the first rectifying element to(V₂′−|V_(th)2); and

[0326] a second step of setting the electric potential of a secondelectrode of the second capacitor means to V₂, making the voltagebetween both electrodes of the first rectifying element converge to thethreshold voltage V_(th)1, and setting the electric potential of thesecond electrode of the first rectifying element to (V₁+V_(th)1).

[0327] According to the present invention, there is provided a method ofdriving a semiconductor device, the semiconductor device comprising:

[0328] a first rectifying element;

[0329] a second rectifying element; and

[0330] capacitor means,

[0331]  characterized in that:

[0332] an electric potential V₁ of a first electric power source isimparted to a first electrode of the first rectifying element;

[0333] a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element;

[0334] a first signal having an electric potential greater than or equalto an electric potential V₂ and less than or equal to an electricpotential V₂′ is input to a second electrode of the second rectifyingelement; and

[0335] a second signal having an electric potential that is greater thanor equal to an electric potential V₃ and less than or equal to (V₃+anelectric potential V_(Data)), or greater than or equal to (V₃−V_(Data))and less than or equal to V₃, is input to a second electrode of thecapacitor means;

[0336] the method of driving the semiconductor device comprising:

[0337] when a threshold voltage of the first rectifying element is takenas V_(th)1 and a threshold voltage of the second rectifying element istaken as V_(th)2,

[0338] a first step of setting the electric potential of the secondelectrode of the second capacitor means to V₂′, and setting the electricpotential of the second electrode of the first rectifying element to(V₂′−|V_(th)2|);

[0339] a second step of setting the electric potential of a secondelectrode of the second capacitor means to V₂, making the voltagebetween both electrodes of the first rectifying element converge to thethreshold voltage V_(th)1, and setting the electric potential of thesecond electrode of the first rectifying element to (V₁+V_(th)1); and

[0340] a third step of changing the electric potential of the secondelectrode of the capacitor means by V_(Data), and setting the electricpotential of the second electrode of the first rectifying element to(V₁+V_(th)1±V_(Data)).

[0341] According to the present invention, there is provided a method ofdriving a semiconductor device, characterized in that:

[0342] the semiconductor device further comprises a transistor; and

[0343] a gate electrode of the transistor is electrically connected tothe second electrode of the first rectifying element.

[0344] According to the present invention, there is provided a method ofdriving a semiconductor device, characterized in that:

[0345] the rectifying element is formed by using a transistor having aconnection between its gate and its drain;

[0346] V₁<V₂ if the transistor having a connection between its gate andits drain is an n-channel transistor; and

[0347] V₁>V₂ if the transistor having a connection between its gate andits drain is a p-channel transistor.

[0348] According to the present invention, there is provided a method ofdriving a semiconductor device, characterized in that:

[0349] the first rectifying element is formed by using a transistorhaving a connection between its gate and its drain;

[0350] V₁<V₂ if the transistor having a connection between its gate andits drain is an n-channel transistor; and

[0351] V₁>V₂ if the transistor having a connection between its gate andits drain is a p-channel transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0352] In the accompanying drawings:

[0353]FIGS. 1A and 1B are diagrams for explaining an embodiment mode ofthe present invention, and operation of the embodiment mode;

[0354]FIGS. 2A to 2E are diagrams for explaining an embodiment mode ofthe present invention, and operation of the embodiment mode;

[0355]FIGS. 3A to 3E are diagrams for explaining an embodiment mode ofthe present invention, and operation of the embodiment mode;

[0356]FIGS. 4A to 4C are diagrams for explaining an embodiment mode ofthe present invention, and operation of the embodiment mode;

[0357]FIGS. 5A to 5C are diagrams for explaining an embodiment mode ofthe present invention, and operation of the embodiment mode;

[0358]FIGS. 6A to 6C are diagrams for explaining an embodiment mode ofthe present invention, and operation of the embodiment mode;

[0359]FIGS. 7A to 7D are diagrams for explaining an embodiment mode ofthe present invention, and operation of the embodiment mode;

[0360]FIG. 8 is a diagram showing the structure of a pixel in a generallight emitting device;

[0361]FIGS. 9A to 9C are diagrams for explaining a method combining adigital gray scale method and a time gray scale method;

[0362]FIGS. 10A and 10B are diagrams for explaining an example of apixel of a light emitting device capable of correcting dispersions inTFT threshold values, and operation of the light emitting device pixel;

[0363]FIGS. 11A to 11F are diagrams for explaining an example of a pixelof a light emitting device capable of correcting dispersions in TFTthreshold values, and operation of the light emitting device pixel;

[0364]FIGS. 12A to 12C are diagrams for explaining operation when amethod combining a digital gray scale method and a time gray scalemethod is used in the present invention;

[0365]FIGS. 13A to 13H are diagrams showing examples of electronicequipment capable of applying the present invention;

[0366]FIGS. 14A to 14E are diagrams for explaining the operatingprinciple of the present invention;

[0367]FIGS. 15A to 15C are an upper surface diagram and cross sectionaldiagrams of a light emitting device; FIGS. 16A and 16B are diagrams forexplaining an embodiment mode of the present invention, and operation ofthe embodiment mode;

[0368]FIGS. 17A to 17E are diagrams for explaining an embodiment mode ofthe present invention, and operation of the embodiment mode;

[0369]FIGS. 18A to 18C are diagrams for explaining an outline of a lightemitting device using an analog signal method;

[0370]FIGS. 19A and 19B are diagrams showing examples of the structureof a source signal line driver circuit and a gate signal line drivercircuit, respectively, used in FIGS. 18A to 18C;

[0371]FIGS. 20A and 20B are diagrams for explaining an outline of alight emitting device using a digital signal method;

[0372]FIGS. 21A and 21B are diagrams showing examples of the structureof a source signal line driver circuit and a gate signal line drivercircuit, respectively, used in FIGS. 20A to 20C;

[0373]FIG. 22 is a diagram showing an example of a layout of pixelshaving the structure shown in FIGS. 1A and 1B;

[0374]FIGS. 23A and 23B are diagrams showing examples of the structureof an electric current source circuit using the threshold valuecorrecting principle of the present invention;

[0375]FIGS. 24A and 24B are diagrams showing examples of the structureof an electric current source circuit using the threshold valuecorrecting principle of the present invention;

[0376]FIGS. 25A and 25B are diagrams showing examples of the structureof an electric current source circuit using the threshold valuecorrecting principle of the present invention; and

[0377]FIGS. 26A and 26B are diagrams showing examples of the structureof an electric current source circuit using the threshold valuecorrecting principle of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0378] Embodiment Mode 1

[0379] Embodiment Mode 1 of the present invention is shown in FIG. 1A.Embodiment Mode 1 has a source signal line 101, a first gate signal line102, a second gate signal line 103, TFTs 104 to 107, capacitor means108, an EL element 109, a reset electric power source line 110, anelectric current supply line 111, and an electric power source line 112.In addition, a storage capacitor means 113 for storing an image signalmay also be formed.

[0380] A gate electrode of the TFT 104 is connected to the first gatesignal line 102, a first electrode of the TFT 104 is connected to thesource signal line 101, and a second electrode of the TFT 104 isconnected to a first electrode of the capacitor means 108. A gateelectrode and a first electrode of the TFT 105 are connected with eachother, and also connected to a second electrode of the capacitor means108. A second electrode of the TFT 105 is connected to the resetelectric power source line 110. A gate electrode of the TFT 106 isconnected to the second electrode of the capacitor means 108, and to thegate electrode and the first electrode of the TFT 105. A first electrodeof the TFT 106 is connected to the electric current supply line 111, anda second electrode of the TFT 106 is connected to a first electrode ofthe EL element 109. A second electrode of the EL element 109 isconnected to the electric power source line 112, and has a mutualelectric potential difference with the electric current supply line 111.A gate electrode of the TFT 107 is connected to the second gate signalline 103, a first electrode of the TFT 107 is connected to the sourcesignal line 101, and a second electrode of the TFT 107 is connected tothe gate electrode of the TFT 106. When forming the storage capacitormeans 113, formation is possible between the gate electrode of the TFT106 and a position at which a fixed electric potential can be obtained,such as the electric current supply line 111.

[0381]FIG. 1B shows the timing at which pulses are input to the firstand the second gate signal lines. Operation is explained using FIGS. 1Aand 1B, and FIGS. 2A to 2D. Note that although a structure is used herewherein the TFTs 104 and 107 are n-channel TFTs, and the TFTs 105 and106 are p-channel TFTs, the TFTs 104 and 107 may have any polarity,provided that they function as simple switching elements.

[0382] The electric potential of the reset electric power source line110 is V_(Reset), and the electric potential of the electric currentsupply line 111 is V_(DD), where V_(Reset)<V_(DD). The electricpotential of the source signal line 101 first becomes V_(SS) (whereV_(SS)<V_(Reset)), and in addition, the second gate signal line 103becomes H level and the TFT 107 turns on. The electric potentials of thegate electrodes of the TFTs 105 and 106 thus drop. The voltage betweenthe gate and the source of the TFT 106 soon becomes less than thethreshold value, and the TFT 106 turns on. The voltage between the gateand the source of the TFT 105 also becomes less than the thresholdvalue, and the TFT 105 also turns on (see FIG. 2A). Although the TFT 104is off in FIG. 2A at this point, it may also be on during this period.

[0383] An electric current path develops from the reset electric powersource line 110 to the TFT 105 to the TFT 107 and to the source signalline 101 when the TFT 105 turns on. The second gate signal line 103therefore becomes L level after the TFT 105 turns on, and the TFT 107turns off. The first gate signal line 102 becomes H level at the sametime, and the TFT 104 turns on. Electric charge thus moves as shown inFIG. 2B. The TFT 105 is on, and therefore the electric potentials of thegate electrodes of the TFTs 105 and 106 increase. The gate and the drainof the TFT 105 are connected here, and therefore the TFT 105 turns offat the point when the voltage between the gate and the source of the TFT105, that is, the voltage between the source and the drain of the TFT105, becomes equal to the threshold value. The electric potentials ofthe gate electrodes of the TFTs 105 and 106 is (V_(Reset)−|V_(th)|) atthis point. In focusing on the capacitor means 108, however, electriccharge accumulates such that the voltage between both electrodes of thecapacitor means 108 becomes (V_(Reset)−|V_(th)1−V_(SS)).

[0384] An image signal is then input from the source signal line 101(see FIG. 2C). The electric potential of the source signal line 101changes by V_(Data) from V_(SS). The electric potentials of the gateelectrodes of the TFTs 105 and 106 also change by V_(Data) due tocapacitive coupling with the capacitor means 108. The TFT 105 should notturn on at this point. Conditions of the values of V_(Data) at thispoint are discussed below. On the other hand, the electric potential ofthe source of the TFT 106 is V_(DD) (where V_(DD)>V_(Reset)), and thevoltage between the gate and the source of the TFT 106 becomes(V_(Reset)−|V_(th)1+V_(Data)−V_(DD)). A drain current corresponding tothe voltage between the gate and the source of the TFT 106 is suppliedto the EL element 109, and light is emitted (see FIG. 2D).

[0385] The relationship between the sizes of the electric potentialV_(Reset) of the reset electric power source line 110, the electricpotential V_(DD) of the electric current supply line 111, the electricpotential of the source signal line 101, and the image signal V_(Data)is explained here using FIG. 2E.

[0386] First of all, the fixed electric potential size relationshipfollows V_(SS)<V_(Reset)<V_(DD).

[0387] Next, consider the electric potentials of the gate electrodes ofthe TFTs 105 and 106. The electric potentials of the gate electrodes ofthe TFTs 105 and 106 become the electric potential shown by symbol [1]in FIG. 2E due to the initialization of FIG. 2A, that is, V_(SS). Theelectric potentials of the gate electrodes of the TFTs 105 and 106 risein the period during which storage of the threshold value is performed,and finally arrive at the electric potential shown by symbol [2] in FIG.2E, that is, (V_(Reset)−|V_(th)|). The electric potentials thenadditionally change by V_(Data) from the potential shown by symbol [2]when the image signal is input. The electric potentials of the gateelectrodes of the TFTs 105 and 106 become lower than the electricpotential of symbol [2] in the case where V_(Data) is a negative value.That is, the voltage between the gate and the source of the TFT 105becomes lower than the threshold value, and the TFT 105 turns on, andthis is contrary to the previous conditions. It is therefore necessaryfor V_(Data) to be a positive value. The electric potentials of the TFTs105 and 106 become electric potentials shown by symbol [3] in FIG. 2Edue to the input image signal, that is, (V_(Reset)−|V_(th)|+V_(Data)).Further, the TFT 106 turns off if the electric potential of the gateelectrode of the TFT 106 becomes higher than V_(DD)−|V_(th)|, andtherefore the range of electric potential values which the image signalV_(Data) is capable of taking is the range denoted by reference numeral200 in FIG. 2E. In other words, it is necessary that the followingrelationship be true: 0≦V_(Data)≦V_(DD)−V_(Reset) (preferably,0<V_(Data)≦V_(DD)−V_(Reset) to ensure that the TFT 105 turns off).However, at a gray scale 0, that is, when the EL element 109 is in astate of absolutely no light emission, an electric potential that isslightly higher than the electric potential at which the TFT 106 turnsoff, in other words, slightly higher than (V_(DD)−V_(Reset)), may beapplied.

[0388] The closer V_(Data) comes to zero at this point, the larger theabsolute value of the voltage between the gate and the source of the TFT106, and therefore the higher the brightness of the EL element 109becomes. The larger V_(Data) becomes, the smaller the absolute value ofthe voltage between the gate and the source of the TFT 106 becomes, andtherefore the brightness of the EL element 109 is low.

[0389] Display of an image is performed by performing the aboveoperations over one screen. Storage of the threshold value isaccomplished in the present invention by using only the capacitor means108, and therefore it is possible to perform accurate correction of thethreshold value without dispersion in the capacitance values influencingthe value of electric current flowing in the EL elements 109, asdiscussed above.

[0390] Embodiment Mode 2

[0391] A digital gray scale method for controlling the EL element 109 inonly two states, one having a brightness of 100% and one a brightness of0%, by using a region in which it is difficult for TFT threshold valuesand the like to influence the on electric current is proposed as amethod differing from the analog gray scale method discussed above. Onlytwo gray scales, white and black, can be achieved by this method, andtherefore multiple gray scales are realized by combining this methodwith a time gray scale method, a surface area gray scale method, or thelike.

[0392] The term time gray scale method refers to a method in which avisible brightness difference can be achieved by utilizing a differencein the amount of time that the EL elements 109 emit light. The operationof this method will be described in detail in another section of thisspecification, and only two states of the EL elements 109, that is,light emission and non-light emission, need to be used with this type ofdriving method. Therefore only two electric potentials need to beimparted by the image signal V_(Data), that is, H level and L level.

[0393] The TFT 106 is a p-channel TFT here, and therefore the EL element109 emits light when V_(Data) is L level, and the EL element 109 doesnot emit light when V_(Data) is H level. From the conditions of V_(Data)shown in Embodiment Mode 1, the electric potential is in the range shownby the reference numeral 200 in FIG. 2E and as much electric current aspossible can be supplied to the EL element 109 at this point whenV_(Data) is L level. In addition, an electric potential at which the TFT105 does not turn on may also be used. In other words, an electricpotential equal to, or slightly greater than, (V_(Reset)−|V_(th)|) maybe used. On the other hand, an electric potential able to ensure thatthe TFT 106 turns off may be used when V_(Data) is H level. It is notparticularly necessary that the electric potential be in the rangedenoted by the reference numeral 200 for this case. Rather, it isdesirable that an electric potential higher than the range denoted bythe reference numeral 200 (for example, V_(DD) or the like) be input.

[0394] Embodiment Mode 3

[0395] An example in which some TFT connections differ is shown in FIG.3A as a third embodiment mode. Although generally similar to thestructure shown in FIG. 1A, there is a difference in that a firstelectrode of a TFT 307 is connected to a second electrode of a TFT 304,not to a source signal line.

[0396] Operation is explained following FIGS. 3B to 3E. The electricpotential of a reset electric power source line 310 is V_(Reset), andthe electric potential of an electric current supply line 311 is V_(DD),such that V_(Reset)<V_(DD). First, the electric potential of a sourcesignal line 301 becomes V_(SS) (where V_(SS)<V_(Reset)), and inaddition, first and second gate signal lines 302 and 303 become H level,while TFTs 304 and 307 turn on. The electric potentials of gateelectrodes of TFTs 305 and 306 thus drop. The voltage between the gateand the source of the TFT 305 soon becomes lower than the thresholdvalue of the TFT 305, which turns on, and the voltage between the gateand the source of the TFT 306 becomes lower than the threshold value ofthe TFT 306, which also turns on (see FIG. 3B).

[0397] An electric current path from the reset electric power sourceline 310 to the TFT 305, to the TFT 307, to the TFT 304, and to thesource signal line 301 develops due to the TFT 305 turning on. Thesecond gate signal line 303 therefore becomes L level immediately afterboth the TFTs 305 and 306 turn on, and the TFT 307 turns off. Movementof electric charge as shown in FIG. 3C thus develops. The TFT 305 is on,and therefore the electric potentials of the gate electrodes of the TFTs305 and 306 rise. The gate and the drain of the TFT 305 are connectedhere, and therefore the TFT 305 turns off at the point when the voltagebetween the gate and the source of the TFT 305, that is the voltagebetween the source and the drain of the TFT 305, becomes equal to thethreshold value V_(th). The electric potentials of the gate electrodesof the TFTs 305 and 306 are (V_(Reset)−|V_(th)|) at this point. Infocusing on the capacitor means 308, however, electric chargeaccumulates by the amount that the electric potential of the secondelectrode changes.

[0398] An image signal is then input from the source signal line 301(see FIG. 3D). The electric potential of the source signal line 301changes by V_(Data) from V_(SS). The electric potentials of the gateelectrodes of the TFTs 305 and 306 also change by V_(Data) due tocapacitive coupling with the capacitor means 308. The TFT 305 does notturn on at this point. On the other hand, the electric potential of thesource of the TFT 306 is V_(DD) (where V_(DD)>V_(Reset)), and thevoltage between the gate and the source of the TFT 306 becomes(V_(Reset)−|V_(th)|+V_(Data)−V_(DD)). A drain current corresponding tothe voltage between the gate and the source of the TFT 306 is suppliedto the EL element 309, and light is emitted (see FIG. 3E).

[0399] Embodiment Mode 4

[0400] A method of combining a digital gray scale method and a time grayscale method is explained here. The structure of a pixel shown in FIG.9A is an example that can be employed by driving with using this type ofmethod. It becomes possible to minutely control the length of timeduring which light is emitted by using an erasure TFT 906 in addition toa switching TFT 904, and a driver TFT 905.

[0401] One frame period is divided into a plurality of subframe periodswhen combining a digital gray scale method and a time gray scale method,as shown in FIG. 9B. Each of the subframe periods has an address (writein) period and a sustain (light emitting) period as shown in FIG. 9C,and in addition, an erasure period if necessary. A method of gray scaleexpression may be used, for example, in which the number of subframeperiods are formed corresponding to the number of display bits, and thelengths of the sustain (light emitting) period in each of the subframeperiods are taken as 2^((n−1)):2^((n−2)): . . . :2:1. Light emission ornon-light emission by the EL element is selected for each sustain (lightemitting) period, and gray scale expression is performed by utilizingthe difference in the lengths of the total time during which the ELelement emits light in one frame period. It is recognized thatbrightness increases with a longer total light emitting period, andbrightness decreases with a shorter total light emitting period. A 4-bitgray scale example is shown in FIG. 9B, and one frame period is dividedinto four subframe periods. By combining the subframe periods withsustain (light emitting) periods, 2⁴⁼¹⁶ gray scales can be expressed.Note that the number of divisions of the frame period is not limited tofour, and that it is also possible to further divide the frame periodinto more subframe periods.

[0402] Further, it is not always necessary that the relative lengths ofthe sustain (light emitting) periods during gray scale expression be2^((n−1)):2^((n−2)): . . . :2:1.

[0403] The length of the sustain (light emitting) period of lower bitsbecomes very short when forming multiple gray scales by this method, andtherefore a period develops, after the sustain (light emitting) periodis complete and the next address period immediately begins, during whichaddress (write in) periods of different subframe periods overlap. Inthis case, an image signal input to a certain pixel is also input at thesame time to different pixels, and correct display therefore cannot beperformed. The erasure period is formed in order to solve this problem,and is formed after Ts3 and Ts4 in FIG. 9B so that address (write in)periods belonging to adjacent subframe periods do not overlap. Erasureperiods are not formed in SF1 and SF2, which have long sustain (lightemitting) periods and in which there is no concern that address (writein) periods belonging to adjacent subframe periods will overlap.

[0404]FIG. 4A shows a method of combining a digital gray scale methodand a time gray scale method, wherein a third gate signal line 414 andan erasure TFT 415 are added to the pixel structure shown in EmbodimentMode 1. A gate electrode of the erasure TFT 415 is connected to thethird gate signal line 414, a first electrode of the erasure TFT 415 isconnected to a gate signal line of a TFT 406, and a second electrode ofthe erasure TFT 415 is connected to an electric current supply line 411.Further, in the case where a storage capacitor means 413 for storing animage signal is formed, it may be formed between a gate electrode of theTFT 406 and a location at which a fixed electric potential can beobtained. The storage capacitor means 413 is formed between the gateelectrode of the TFT 406 and the electric current supply line 411 inFIGS. 4A to 4C, but it may also be formed, for example, between the gateelectrode of the TFT 406 and a prior stage gate signal line. Further, itmay also be formed between a second electrode of the TFT 404 and a fixedelectric potential such as the electric current supply line 411, and itmay be formed on both if there is a desire to make the storagecapacitance larger.

[0405] Operations from initialization, to input of an image signal, andto light emission is similar to the explanation provided in EmbodimentMode 1. Note that the erasure TFT 415 is off during initialization,input of the image signal, and the sustain (light emitting) period.

[0406] Operation from the sustain (light emitting) period to the erasureperiod is explained here using FIGS. 4A to 4C, and FIGS. 12A to 12C.FIG. 12A is similar to the diagram shown in FIG. 9B, and one frameperiod has four subframe periods. Subframe periods SF3 and SF4, whichhave short sustain (light emitting) periods, each have erasure periodsTe3 and Te4, as shown in FIG. 12B. Operation during the sustain periodSF3 is taken as an example here for explanation.

[0407] Electric current corresponding to the voltage between the gateand the source of the TFT 406 flows in the EL element 409 as shown inFIG. 4B after input of the image signal is complete. A pulse is theninput to the third gate signal line 414 when a timing for completion ofthe corresponding sustain (light emitting) period is complete, the thirdgate signal line 416 becomes H level, and the TFT 415 turns on. Thevoltage between the gate and the source of the TFT 406 is zero, as shownin FIG. 4C. The TFT 406 thus turns off by this operation, and electriccurrent to the EL element 409 is cut off. The EL element 409 istherefore forcibly placed in a non-light emitting state.

[0408] The timing chart for these operations is shown in FIG. 12C.Periods for performing initialization, threshold value storage, andwrite in of the image signal are contained in the address (write in)period. A period beginning after a pulse is input to the third gatesignal line 414 after the sustain (light emitting) period and the ELelement 409 becomes non-light emitting, up through when a pulse is nextinput to the second gate signal line 403 and initialization begins, isthe erasure period.

[0409] Embodiment Mode 5

[0410] An example of performing erasure operations using a structurethat differs from the structure of Embodiment Mode 4 is explained usingFIGS. 5A to 5C in Embodiment Mode 5.

[0411]FIG. 5A shows a structure having the erasure TFT 415, similar toEmbodiment Mode 4. However, although the first electrode of the TFT 415is connected to the gate electrode of the TFT 406, namely to a secondelectrode of capacitor means 408 in Embodiment Mode 4, the firstelectrode of the TFT 415 is connected to a first electrode of thecapacitor means 408 in FIG. 5.

[0412] Electric current corresponding to the voltage between the gateand the source of the TFT 406 flows in the EL element 409 as shown inFIG. 5B after input of the image signal is complete. A pulse is theninput to the third gate signal line 414, which becomes H level, when atiming for completion of the corresponding sustain (light emitting)period is reached, and the TFT 415 turns on. The electric potential ofthe first electrode of the capacitor means 408 becomes V_(DD), as shownin FIG. 5C. The electric potential of the gate electrode of the TFT 406consequently becomes higher than V_(DD), and therefore the voltagebetween the gate and the source becomes a positive value. The TFT 406thus turns off by this operation, electric current to the EL element 409is cut off, and the EL element 409 is forcibly placed in a non-lightemitting state.

[0413] Operations during the erasure period are such that electriccurrent to the EL element 409 is cut off by making the voltage betweenthe gate and the source of the TFT 406, which functions as a driver TFTin order to supply electric current to the EL element 409, a voltage atwhich the TFT 406 turns off. Provided that operation is based upon thisprinciple, there are no limitations placed on the placement of theerasure TFT 415.

[0414] Embodiment Mode 6

[0415] Operation during the erasure period in Embodiment Modes 4 and 5is such that electric current to the EL element 409 is cut off by makingthe voltage between the gate and the source of the TFT 406, whichfunctions as a driver TFT for supplying electric current to the ELelement 409, a voltage at which the TFT 406 turns off. An example ofusing another method is shown in FIG. 6A. The erasure TFT 415 is formedbetween the electric current supply line 411 and the gate electrode ofthe TFT 406, or between the electric current supply line 411 and thefirst electrode of the capacitor means 408 in Embodiment Modes 4 and 5.However, the erasure TFT 415 is formed between the TFT 406 and the ELelement 409 in Embodiment Mode 6. That is, a TFT is added in any placeof the pathway from the electric current supply line to the TFT 406 andto the EL element 409 with the method of Embodiment Mode 6, and thesupply of electric current to the EL element 409 is cut off by turningthis TFT off.

[0416] Initialization, input of an image signal, and light emission aresimilar to those of Embodiment Modes 4 and 5. However, the erasure TFT415 is on only during the sustain (light emitting) period, and electriccurrent flows as shown in FIG. 6B. The TFT 415 is off duringinitialization, input of the image signal, and during the erasureperiod, and electric current to the EL element 409 is cut off duringthese periods.

[0417] Differences in operation between Embodiment Mode 6 and EmbodimentModes 4 and 5 are explained. The voltage between the gate and the sourceof the TFT 406 is controlled by turning the erasure TFT 415 on once inEmbodiment Modes 4 and 5, and therefore the EL element 409 does not emitlight after this operation is performed until the next image signal iswritten in. Consequently, pulses input to the third gate signal line 414may be short pulses input at a timing at which the erasure periodbegins, as shown in FIG. 12C. In Embodiment Mode 6, however, it isnecessary for the erasure TFT 415 to be on throughout the sustain (lightemitting) period, and therefore it is necessary to input pulses to thethird gate signal line 415, the pulses lengths equal to the sustain(light emitting) periods, for each of the subframe periods.

[0418] Further, although the erasure TFT 415 uses an n-channel TFT inEmbodiment Modes 4, 5, and 6, there are no particular limitations placedon the polarity in Embodiment Mode 6 because the erasure TFT 415functions solely as a switching element.

[0419] Embodiment Mode 7

[0420] Initialization operations prior to the input of image signals areperformed by using a certain TFT in Embodiment Modes 1 to 6.Specifically, a threshold value appearing between the source and thedrain of a TFT, which has a connection between a gate electrode and adrain electrode, is obtained. In contrast, a diode 713 is used as asubstitute for the TFT in FIG. 7A. A first electrode of the diode 713 isconnected to a gate electrode of a TFT 706, and a second electrode ofthe diode 713 is connected to a second gate signal line 703. Further, ifcapacitor means 712 is formed in order to store image signals, then thecapacitor means may be formed between the gate electrode of the TFT 706and a location at which a fixed electric potential can be obtained, suchas an electric current supply line 710. Furthermore, the capacitor means712 may also be formed between a second electrode of a TFT 704 and alocation at which a fixed electric potential can be obtained, such asthe electric current supply line 710. The capacitor means may also beformed in both locations if a large value of storage capacitance isdesired.

[0421] Only operations during initialization differ from EmbodimentMode 1. Explanations regarding input of an image signal and lightemitting operations are omitted here. Operations during initializationare explained using FIG. 7B.

[0422] First, the electric potential of the second gate signal line 703is set to H level (for example, V_(DD)). A forward bias is then impartedto the diode 713 if the electric potential of the second gate signalline 702 is set to L level (for example, V_(SS)) at the initializationtiming. Electric current develops as shown in FIG. 7B from nodes havinga high electric potential to nodes having a low electric potential, andthe electric potential of a gate electrode of a TFT 705, and theelectric potential of the gate electrode of the TFT 706, drop Thevoltage between the gate and the source of the TFT 705 soon becomeslower than the threshold voltage, and the TFT 705 turns on. Thereafter,the voltage between the gate and the source of the TFT 706 becomes lowerthan the threshold voltage, and the TFT 706 also turns on.Initialization is complete at this point, and the electric potential ofthe second gate signal line 703 once again becomes H level. A reversebias is imparted to the diode 713 at this point, and electric currentdoes not flow during periods for performing image signal input and lightemission operations.

[0423] Electric current corresponding to the input image signal thenflows in the EL element 708, and the EL element 708 emits light, similarto Embodiment Mode 1.

[0424]FIG. 7C shows an example of forming capacitor means 714 as asubstitute for the diode 713. A first electrode of the capacitor means714 is connected to the gate electrode of the TFT 706, and a secondelectrode of the capacitor means 714 is connected to the second gatesignal line 703. Also in this case, operation is similar to that shownin FIG. 7B. First, the second gate signal line 703 is set to H level,and the electric potential of the second gate signal line 703 is set toL level at the initialization timing. The TFT 705 turns off at thispoint, and therefore the electric potentials of the gate electrodes ofthe TFTs 705 and 706 drop due to capacitive coupling with the capacitormeans 714. The voltage between the gate and the source of the TFT 705soon becomes lower than the threshold voltage, and the TFT 705 turns on.The voltage between the gate and the source of the TFT 706 then becomeslower than the threshold voltage, and the TFT 706 also turns on.

[0425] The TFT 704 then turns on, and input of an image signal isperformed. The second gate signal line 703 is L level at this point, butmay also be set to H level during input of the image signal.

[0426] Electric current corresponding to the input image signal thenflows in the EL element 708, and the EL element 708 emits light, similarto Embodiment Mode 1.

[0427] Embodiment Mode 8

[0428] Display devices having an integrally formed pixel portion andperipheral circuits, formed by TFTs and the like built into a substrate,have the advantages of small size and light weight. However, theirmanufacturing processes are complex, such as element formation byrepeatedly performing film formation and etching, and the addition ofimpurity elements for imparting conductivity to semiconductor layers. Inparticular, processes for adding impurity elements differ betweenp-channel TFTs and n-channel TFTs, and this therefore invites furtherincreases of processing.

[0429] Processes for adding impurity elements can be partly omitted bystructuring the pixel portion and the peripheral circuits using TFTshaving a single polarity. Not only does it thus become possible toshorten processing, but the number of photomasks can also be reduced.

[0430] An example of a structure that uses TFTs having a single polaritytype is the structure disclosed in Japanese Patent Application No.2001-348032 by the applicants of the present invention. This is astructure in which only n-channel TFTs having a high field-effectmobility are used, and in addition, a structure in which drops inbrightness do not easily occur, even if EL elements deteriorate.

[0431] A structure provided with both advantages, that is a structure inwhich drops in brightness following deterioration of EL elements arecontrolled, and one in which correction of dispersion in TFT thresholdvalues is possible, is explained in Embodiment Mode 8 by combining theaforementioned technique with the present invention.

[0432]FIG. 16A shows an example structure. The structure has a sourcesignal line 1601, a first gate signal line 1602, a second gate signalline 1603, a third gate signal line 1604, TFTs 1605 to 1609, capacitormeans 1610 and 1611, an EL element 1612, a reset electric power sourceline 1613, an electric current supply line 1614, and electric powersource lines 1615 and 1616. If a storage capacitor means 1617 is formed,it may be formed between a gate electrode of the TFT 1607 and a locationat which a fixed electric potential can be obtained, such as theelectric current supply line 1614.

[0433] A gate electrode of the TFT 1605 is connected to the first gatesignal line 1602, a first electrode of the TFT 1605 is connected to thesource signal line 1601, and a second electrode of the TFT 1605 isconnected to a first electrode of the capacitor means 1610. A gateelectrode and a first electrode of the TFT 1606 are connected with eachother, and then connected to a second electrode of the capacitor means1610. A second electrode of the TFT 1606 is connected to the resetelectric power source line 1613. The gate electrode of the TFT 1607 isconnected to the gate electrode and the first electrode of the TFT 1606.A first electrode of the TFT 1607 is connected to the electric currentsupply line 1614, and a second electrode of the TFT 1607 is connected toa first electrode (anode) of the EL element 1612. A gate electrode ofthe TFT 1608 is connected to the second gate signal line 1603, a firstelectrode of the TFT 1608 is connected to the source signal line 1601,and a second electrode of the TFT 1608 is connected to the gateelectrodes of the TFTs 1606 and 1607. A gate electrode of the TFT 1609is connected to the third gate signal line 1604, a first electrode ofthe TFT 1609 is connected to the electric power source line 1616, and asecond electrode of the TFT 1609 is connected to the first electrode(anode) of the EL element 1612. A second electrode (cathode) of the ELelement 1612 is connected to the electric power source line 1615. Afirst electrode of the capacitor means 1611 is connected to the secondelectrode of the TFT 1605, and a second electrode of the capacitor means1611 is connected to the first electrode (anode) of the EL element 1612.

[0434] Operation is explained following FIG. 16B and FIGS. 17A to 17E. Atiming chart for pulses input into the first to the third gate signallines 1602 to 1604, and for an image signal input to the source signalline 1601 is shown in FIG. 16B. The image signal is input at a timingdenoted by symbol “V”, and at a predetermined electric potential.

[0435] The electric potential of the reset electric power source line1613 is V_(Reset), the electric potential of the electric current supplyline 1614 is V_(DD), the electric potential of the electric power sourceline 1615 is V_(C), and the electric potential of the electric powersource line 1616 is V_(SS), where V_(SS)<V_(C)<V_(DD)<V_(Reset). First,the electric potential of the source signal line 1601 is set to V_(x)(where V_(x)>V_(Reset)). The second gate signal line 1603 and the thirdgate signal line 1604 then become H level, the TFTs 1608 and 1609 bothturn on, an electric current develops as shown in FIG. 17A, and theelectric potentials of the gate electrodes of the TFTs 1606 and 1607rise. The voltage between the gate and the source of the TFT 1606 soonrises above the threshold value, and the TFT 1606 turns on. In addition,the voltage between the gate and the source of the TFT 1607 rises abovethe threshold value, and the TFT 1607 turns on. Initialization is thuscomplete by the above operations.

[0436] The second gate signal line becomes L level immediately afterinitialization is complete, and the TFT 1608 turns off. The electricpotentials of the gate electrodes of the TFTs 1606 and 1607 thus beginto drop. The TFT 1606 turns off at the point where the electricpotential becomes (V_(Reset)+V_(th)), that is when the voltage betweenthe gate and the source of the TFT 1606 becomes equal to the thresholdvalue. An electric potential difference thus develops between bothelectrodes of the capacitor means 1610, and this electric potentialdifference is stored.

[0437] On the other hand, the voltage between the gate and the source ofthe TFT 1607 at this point exceeds the threshold value, and thereforethe TFT 1607 turns on. The TFT 1609 also turns on, and thereforeelectric current flows as shown in FIG. 17B in a pathway from theelectric current supply line 1614, to the TFT 1607, to the TFT 1609, andto the electric power source line 1616. Electric current does not flowin the EL element 1612 at this point, however, because V_(SS)<V_(C). TheEL element 1612 therefore does not emit light.

[0438] Input of an image signal begins next. An image signal having apredetermined electric potential is input to the source signal line1601, which is fixed to the electric potential V_(x), and the electricpotential of the source signal line 1601 becomes (V_(x)−V_(Data)). Thevoltage between the gate and the source of the TFT 1606 becomes lowerthan the threshold value, and the TFT remains off. On the other hand,the voltage between the gate and the source of the TFT 1607 becomes(V_(Reset)+V_(th)−V_(Data)−V_(DD)), and a drain current corresponding tothis voltage flows (see FIG. 17C).

[0439] The first gate signal line 1602 becomes L level when input of theimage signal is complete, and the TFT 1605 turns off. The third gatesignal line 1604 then becomes L level, and the TFT 1609 turns off.Electric current flowing in the TFT 1607 thus flows in the EL element1612, and light is emitted (see FIG. 17D).

[0440] An explanation regarding the relationship between the sizes ofthe electric potential V_(Reset) of the reset electric power source line1613, the electric potential V_(DD) of the electric current supply line1614, the electric potential of the source signal line 1601, and theimage signal V_(Data) is made here using FIG. 17E.

[0441] Consider the electric potentials of the gate electrodes of theTFTs 1606 and 1607. The electric potentials of the gate electrodes ofthe TFTs 1606 and 1607 become the electric potential denoted by symbol[1] in FIG. 17E due to the initialization of FIG. 17A. That is, theelectric potentials become V_(x). The electric potentials of the gateelectrodes of the TFTs 1606 and 1607 drop during a period for performingstorage of the threshold values, and finally become the electricpotential denoted by symbol [2] in FIG. 17E. That is, the electricpotentials become (V_(Reset)+|V_(th)|). Subsequently, when an imagesignal is input, the electric potentials of the gate electrodes of theTFTs 1606 and 1607 further change by V_(Data) from the electricpotential of symbol [2]. The electric potentials of the gate electrodesof the TFTs 1606 and 1607 becomes higher than the electric potential ofsymbol [2] here in the case where the change is positive. That is, thevoltage between the gate and the source of the TFT 1606 becomes higherthan the threshold voltage, and the TFT 1606 turns on, which is contraryto the prior conditions. It is therefore necessary that the change tothe image signal be negative. The electric potentials of the TFTs 1606and 1607 therefore become an electric potential denoted by symbol [3] inFIG. 17E due to the input of the image signal. That is, the electricpotentials become (V_(Reset)+|V_(th)|−V_(Data)). Further, the electricpotential of the gate electrode of the TFT 1607 becomes lower thanVDD+|V_(th)|, and the TFT 1607 turns off, and therefore a range ofelectric potentials at which the image signal V_(Data) can be obtainedis a range denoted by reference numeral 1700 in FIG. 17E. That is, it isnecessary that 0≦V_(Data)≦V_(Reset)−V_(DD) (preferably0<V_(Data)≦V_(Reset)−V_(DD) in order to ensure that the TFT 1606 isoff). However, at a gray scale of zero, namely when the EL element 1612is in a non-light emitting state, an electric potential slightly largerthan (V_(Reset)−V_(DD)) may also be imparted as V_(Data) so as to ensurethat the TFT 1607 turns off.

[0442] The closer V_(Data) is to zero at this point, the higher theabsolute value of the voltage between the gate and the source of the TFT1607 becomes, and therefore the higher the brightness of the EL element1612 becomes. The larger V_(Data) becomes, the smaller the absolutevalue of the voltage between the gate and the source of the TFT 1607,and therefore the lower the brightness of the EL element 1612 becomes.

[0443] The above explanation is made for an example of performingdisplay by an analog gray scale method, but display by a digital grayscale method like that disclosed by Embodiment Mode 2 can also besimilarly made. Further, it is easy to combine Embodiment Mode 8 with astructure in which an erasure TFT is formed when using a time gray scalemethod.

[0444] Embodiments

[0445] Hereafter, the embodiments of the invention will be described.

[0446] Embodiment 1

[0447] In this embodiment, the configuration of a light-emitting devicein which analog video signals are used for video signals for displaywill be described. A configuration example of the light-emitting deviceis shown in FIG. 18A. The device has a pixel portion 1802 wherein aplurality of pixels is arranged in a matrix shape over a substrate 1801,and it has a source signal line driver circuit 1803 and first and secondgate signal line driver circuits 1804 and 1805 around the pixel portion.In FIG. 18A, two couples of gate signal line driver circuits are used,which control first and second gate signal lines.

[0448] Signals inputted to the source signal line driver circuit 1803,and the first and second gate signal line driver circuits 1804 and 1805are provided from outside through a flexible printed circuit (FPC) 1806.

[0449]FIG. 18B shows a configuration example of the source signal linedriver circuit. This is the source signal line driver circuit for usinganalog video signals for video signals for display, which has a shiftregister 1811, a buffer 1812, and a sampling circuit 1813. Not shownparticularly, but a level shifter may be added if necessary.

[0450] The operation of the source signal line driver circuit will bedescribed. FIG. 19A shows the more detailed configuration, thusreferring to the drawing.

[0451] A shift register 1901 is formed of a plurality of flip-flopcircuits (FF) 1902, to which the clock signal (S-CLK), the clockinverted signal (S-CLKb), and the start pulse (S-SP) are inputted. Inresponse to the timing of these signals, sampling pulses are outputtedsequentially.

[0452] The sampling pulses outputted from the shift register 1901 arepassed through a buffer 1903 etc. and amplified, and then inputted to asampling circuit. The sampling circuit 1904 is formed of a plurality ofsampling switches (SW) 1905, which samples video signals in a certaincolumn in accordance with the timing of inputting the sampling pulses.More specifically, when the sampling pulses are inputted to the samplingswitches, the sampling switches 1905 are turned on. The potential heldby the video signals at this time is outputted to the respective sourcesignal lines through the sampling switches.

[0453] Subsequently, the operation of the gate signal line drivercircuit will be described. FIG. 19B shows the more detailedconfiguration of the first and second gate signal line driver circuits1804 and 1805 shown in FIG. 18C. The first gate signal line drivercircuit has a shift register circuit 1911, and a buffer 1912, which isdriven in response to the clock signal (G-CLK1), the clock invertedsignal (G-CLKb1), and the start pulse (G-SP1). The second gate signalline driver circuit 2405 may have a same configuration.

[0454] The operation from the shift register to the buffer is the sameas that in the source signal line driver circuit. The selecting pulsesamplified by the buffer select respective gate signal lines for them.The first gate signal line driver circuit sequentially selects firstgate signal lines G₁₁, G₂₁, . . . and G_(m1), and the second gate signalline driver circuit sequentially selects second gate signal lines G₁₂,G₂₂, . . . and G_(m2). A third gate signal line driver circuit, notshown, is also the same as the first and second gate signal line drivercircuits, sequentially selecting third gate signal lines G₁₃, G₂₃, . . .and G_(m3). In the selected row, video signals are written in the pixelto emit light according to the procedures described in the embodimentmode.

[0455] Note that, as one example of the shift register that formed of aplurality of D-flip-flops is shown here. However, such the configurationis acceptable that signal lines can be selected by a decoder and thelike.

[0456] Embodiment 2

[0457] In this embodiment, a configuration of a light-emitting device inwhich digital video signals are used for video signals for display willbe described. FIG. 20A shows a configuration example of thelight-emitting device. The device has a pixel portion 2002 wherein aplurality of pixels is arranged in a matrix shape over a substrate 2001,and it has a source signal line driver circuit 2003, and first andsecond gate signal line driver circuits 2004 and 2005 around the pixelportion. In FIG. 20A, two couples of gate signal line driver circuitsare used, which control first and second gate signal lines.

[0458] Signals inputted to the source signal line driver circuit 2003,and the first and fourth gate signal line driver circuits 2004 and 2005are supplied from outside through a flexible printed circuit (FPC) 2006.

[0459]FIG. 20B shows a configuration example of the source signal linedriver circuit. This is the source signal line driver circuit for usingdigital video signals for video signals for display, which has a shiftregister 2011, a first latch circuit 2012, a second latch circuit 2013,and a D/A converter circuit 2014. Not shown in the drawing particularly,but a level shifter may be added if necessary.

[0460] The first and second gate signal line driver circuits 2004 and2005 can be same as those shown in Embodiment 1, thus omitting theillustration and description here.

[0461] The operation of the source signal line driver circuit will bedescribed. FIG. 21A shows the more detailed configuration, thusreferring to the drawing.

[0462] A shift register 2101 is formed of a plurality of flip-flopcircuits (FF) 2110 or the like, to which the clock signal (S-CLK), theclock inverted signal (S-CLKb), and the start pulse (S-SP) are inputted.Sampling pulses are sequentially outputted in response to the timing ofthese signals.

[0463] The sampling pulses outputted from the shift register 2101 areinputted to first latch circuits 2102. Digital video signals are beinginputted to the first latch circuits 2102. The digital video signals areheld at each stage in response to the timing of inputting the samplingpulses. Here, the digital video signals are inputted by three bits. Thevideo signals at each bit are held in the respective first latchcircuits. Here, three first latch circuits are operated in parallel byone sampling pulse.

[0464] When the first latch circuits 2102 finish to hold the digitalvideo signals up to the last stage, latch pulses are inputted to secondlatch circuits 2103 during the horizontal retrace period, and thedigital video signals held in the first latch circuits 2102 aretransferred to the second latch circuits 2103 all at once. After that,the digital video signals held in the second latch circuits 2103 for onerow are inputted to D/A converter circuits 2104 simultaneously.

[0465] While the digital video signals held in the second latch circuits2103 are being inputted to D/A converter circuits 2104, the shiftregister 2101 again outputs sampling pulses. Subsequent to this, theoperation is repeated to process the video signals for one frame.

[0466] The D/A converter circuits 2104 convert the inputted digitalvideo signals from digital to analog and output them to the sourcesignal lines as the video signals having the analog voltage.

[0467] The operation described above is conducted throughout the stagesduring one horizontal period. Accordingly, the video signals areoutputted to the entire source signal lines.

[0468] Note that, as described in the Embodiment 1, such theconfiguration is acceptable that a decoder or the like is used insteadof the shift register to select signal lines.

[0469] Embodiment 3

[0470] In Embodiment 2, the digital video signal is subjected todigital-to-analog conversion by the D/A converting circuit and writteninto the pixel. The light-emitting device of the present invention canalso conduct gradation representation by a time gradation method. Inthis case, as shown in FIG. 21B, the D/A converting circuit is notrequired and the gradation representation is controlled according to alength of a light emitting time of the EL element. Thus, it isunnecessary to parallel-process video signals of respective bits so thatthe first and second latch circuits each may also have one bit. At thistime, with respect to the digital video signal, each bit is seriallyinputted, held in succession in the latch circuit, and written into thepixel. Of course, the latch circuit of the required number of bits maybe provided in parallel.

[0471] Embodiment 4

[0472] In this embodiment, an example in which a light-emitting deviceis manufactured according to the present invention will be describedusing FIGS. 15A to 15C.

[0473]FIG. 15A is a top view of a light-emitting device produced bysealing an element substrate in which TFTs are formed with a sealingmember. FIG. 15B is a cross sectional view along a line A-A′ in FIG.15A. FIG. 15C is a cross sectional view along a line B-B′ in FIG. 15A.

[0474] A seal member 4009 is provided to surround a pixel portion 4002,a source signal line driver circuit 4003, and first and second gatesignal line driver circuits 4004 a and 4004 b which are provided on asubstrate 4001. In addition, a sealing member 4008 is provided over thepixel portion 4002, the source signal line driver circuit 4003, and thefirst and second gate signal line driver circuits 4004 a and 4004 b.Thus, the pixel portion 4002, the source signal line driver circuit4003, and the first and second gate signal line driver circuits 4004 aand 4004 b are sealed with the substrate 4001, the seal member 4009 andthe sealing member 4008 and filled with a filling agent 4210.

[0475] Also, the pixel portion 4002, the source signal line drivercircuit 4003, and the first and second gate signal line driver circuits4004 a and 4004 b which are provided on the substrate 4001 each have aplurality of TFTs. In FIG. 15B, TFTs (note that an N-channel TFT and aP-channel TFT are shown here) 4201 included in the source signal linedriver circuit 4003 and a TFT 4202 included in the pixel portion 4002,which are formed on a base film 4010 are typically shown.

[0476] An interlayer insulating film (planarization film) 4301 is formedon the TFTs 4201 and 4202, and a pixel electrode (anode) 4203electrically connected with the drain of the TFT 4202 is formed thereon.A transparent conductive film having a large work function is used asthe pixel electrode 4203. A compound of indium oxide and tin oxide, acompound of indium oxide and zinc oxide, zinc oxide, tin oxide, orindium oxide can be used for the transparent conductive film. Inaddition, the transparent conductive film to which gallium is added maybe used.

[0477] An insulating film 4302 is formed on the pixel electrode 4203. Anopening portion is formed in the insulating film 4302 on the pixelelectrode 4203. In the opening portion, an organic light-emitting layer4204 is formed on the pixel electrode 4203. An organic light emittingmaterial or an inorganic light emitting material that is known can beused as the organic light-emitting layer 4204. In addition, the organiclight emitting material includes a to low molecular weight based(monomer system) material and a high molecular weight based (polymersystem) material, and any material may be used.

[0478] An evaporation technique or an applying method technique that isknown is preferably used as a method of forming the organiclight-emitting layer 4204. In addition, a laminate structure or a singlelayer structure which is obtained by freely combining a hole injectionlayer, a hole transporting layer, a light emitting layer, an electrontransporting layer, and an electron injection layer is preferably usedas the structure of the organic light emitting layer.

[0479] A cathode 4205 made from a conductive film having a lightshielding property (typically, a conductive film containing mainlyaluminum, copper, or silver, or a laminate film of the conductive filmand another conductive film) is formed on the organic light emittinglayer 4204. In addition, it is desirable that moisture and oxygen thatexist in an interface between the cathode 4205 and the organiclight-emitting layer 4204 are minimized.

[0480] Thus, a devise is required in which the organic light emittinglayer 4204 is formed in a nitrogen atmosphere or a noble atmosphere andthe cathode 4205 without being exposed to oxygen and moisture is formed.In this embodiment, the above film formation is possible by using amulti-chamber type (cluster tool type) film formation apparatus. Apredetermined voltage is supplied to the cathode 4205.

[0481] By the above steps, a light-emitting element 4303 composed of thepixel electrode (anode) 4203, the organic light emitting layer 4204, andthe cathode 4205 is formed. A protective film 4209 is formed on theinsulating film 4302 so as to cover the light-emitting element 4303. Theprotective film 4209 is effective to prevent oxygen, moisture, and thelike from penetrating the light-emitting element 4303.

[0482] Reference numeral 4005 a denotes a lead wiring connected with apower source, which is connected with a first electrode of the TFT 4202.The lead wiring 4005 a is passed between the seal member 4009 and thesubstrate 4001 and electrically connected with an FPC wiring 4301 of anFPC 4006 through an anisotropic conductive film 4300.

[0483] A glass material, a metallic member (typically, a stainlessmember), a ceramic member, a plastic member (including a plastic film)can be used as the sealing member 4008. An FRP (fiberglass reinforcedplastic) plate, a PVF (polyvinyl fluoride) film, a Mylar film, apolyester film, or an acrylic resin film can be used as the plasticmember. In addition, a sheet having a structure in which aluminum foilis sandwiched by a PVF film and a Mylar film can be used.

[0484] Note that, it is required that the cover member is transparent tothe light when the light generated at the light-emitting element isemitted through a cover member side. In this case, a transparentmaterial such as a glass plate, a plastic plate, a polyester film, oracrylic film is used.

[0485] Also, in addition to an inert gas such as nitrogen or argon,ultraviolet curable resin or thermal curable resin can be used for thefilling agent 4103. PVC (polyvinyl chloride), acrylic, polyimide, epoxyresin, silicon resin, PVB (polyvinyl butyral), or EVA (ethylene vinylacetate) can be used. In this embodiment, nitrogen is used for thefilling agent.

[0486] Also, in order to expose the filling agent 4103 to a hygroscopicmaterial (preferably barium oxide) or a material capable of absorbingoxygen, a concave portion 4007 is provided to the surface of the sealingmember 4008 in the substrate 4001 side, and the hygroscopic material orthe material capable of absorbing oxygen which is indicated by 4207 islocated. In order to prevent the material 4207 having a hygroscopicproperty or being capable of absorbing oxygen from flying off, thematerial 4207 having a hygroscopic property or being capable ofabsorbing oxygen is held in the concave portion 4007 by a concave covermember 4208. Note that concave cover member 4208 is formed in a finemeshed shape and constructed such that it transmits air and moisture butdoes not transmit the material 4207 having a hygroscopic property orbeing capable of absorbing oxygen. When the material 4207 having ahygroscopic property or being capable of absorbing oxygen is provided,the deterioration of the light-emitting element 4303 can be suppressed.

[0487] As shown in FIG. 15C, a conductive film 4203 a is formed on thelead wiring 4005 a such that it is in contact with the lead wiring 4005a simultaneously with the formation of the pixel electrode 4203.

[0488] Also, the anisotropic conductive film 4300 has a conductivefiller 4300 a. When the substrate 4001 and the FPC 4006 are bonded toeach other by thermal compression, the conductive film 4203 a locatedover the substrate 4001 and the FPC wiring 4301 located on the FPC 4006are electrically connected with each other through the conductive filler4300 a.

[0489] Embodiment 5

[0490] An example of manufacturing pixels actually by using theconfiguration shown in FIG. 1A is demonstrated with reference to FIG.22. A portion surrounded by a dotted line frame 2200 represents onepixel. Another figure numbers are the same as those assigned in FIG. 1A.

[0491] A source signal line 101, a reset power source line 110, and acurrent supply line 111 are formed by using a same layer material forforming a gate electrode. First and second gate signal lines 102 and 103are formed by using a wiring material.

[0492] The pixel electrode 120 serves as a transparent electrode here,and connects to a drain electrode of TFT 106. The pixel electrode 120and the drain electrode of TFT 106 contact each other without through acontact hole by means of overlapping directly a transparent conductivefilm forming a pixel electrode 120 and wiring materials. Of course,another method may be used to contact the drain electrode of TFT 106 andthe pixel electrode 120.

[0493] Though a capacity device 108 and a retention capacity device 113are formed at between the gate materials and the wiring materials, it isnot especially limited to this type. For ease of illustration, a channellength L and a channel width W of TFTs 104 to 107 are not illustrated asto correspond to the actual sizes. It is possible that the desired sizeof L and W is determined at the designing phase and that each TFTdiffers in size.

[0494] Embodiment 6

[0495] A light-emitting device using a light-emitting element is a selflight emission type. Thus, such a light-emitting device has highvisibility in a light place and a wide viewing angle, as compared with aliquid crystal display. Therefore, it can be used for a display portionof various electronic apparatuses.

[0496] As electronic apparatuses using the light-emitting device of thepresent invention, there are a video camera, a digital camera, a goggletype display (head mount display), a navigation system, a soundreproducing device (car audio system, audio component system, or thelike), a laptop computer, a game machine, a portable informationterminal (mobile computer, mobile telephone, portable game machine, anelectric book, or the like), an image reproducing device including arecording medium (specifically, apparatus for reproducing an image froma recording medium such as a digital versatile disc (DVD), whichincludes a display capable of displaying the image), and the like. Inparticular, in the case of the portable information terminal in which ascreen is viewed from an oblique direction in many cases, it isimportant that a view angle is large. Thus, it is desirable that thelight-emitting device is used. Concrete examples of those electronicapparatuses are shown in FIGS. 13A to 13H.

[0497]FIG. 13A shows a light emitting element display device whichincludes a cabinet 3001, a support base 3002, a display portion 3003, aspeaker portion 3004, and a video input terminal 3005. Thelight-emitting device of the present invention can be used for thedisplay portion 3003. The light-emitting device is a self light emissiontype and thus does not require a back light. Therefore, a thinnerdisplay portion than a liquid crystal display can be obtained. Note thatthe light-emitting element display device includes all display devicesfor information display such as personal computer, TV broadcastreceiving, and advertisement display.

[0498]FIG. 13B is a digital still camera, which is composed of a mainbody 3101, a display portion 3102, an image-receiving portion 3103,operation keys 3104, external connection ports 3105, a shutter 3106, andthe like. The light-emitting device of the present invention can be usedin the display portion 3102.

[0499]FIG. 13C is a laptop computer, which is composed of a main body3201, a frame 3202, a display portion 3203, a keyboard 3204, externalconnection ports 3205, a pointing mouse 3206, and the like. Thelight-emitting device of the present invention can be used in thedisplay portion 3203.

[0500]FIG. 13D is a mobile computer, which is composed of a main body3301, a display portion 3302, a switch 3303, operation keys 3304, aninfrared port 3305, and the like. The light-emitting device of thepresent invention can be used in the display portion 3302.

[0501]FIG. 13E is a portable image reproducing device equipped with arecording medium (specifically, a DVD player), and is composed of a mainbody 3401, a frame 3402, a display portion A 3403, a display portion B3404, a recording medium (such as a DVD) read-in portion 3405, operationkeys 3406, a speaker portion 3407, and the like. The display portion A3403 mainly displays image information, and the display portion B 3404mainly displays character information, and the light-emitting device ofthe present invention can be used in the display portion A 3403 and inthe display portion B 3404. Note that family game machines and the likeare included in the category of image reproducing devices provided witha recording medium.

[0502]FIG. 13F is a goggle type display device (head mounted display),which is composed of a main body 3501, a display portion 3502, and anarm portion 3503. The light-emitting device of the present invention canbe used in the display portion 3502.

[0503]FIG. 13G is a video camera, which is composed of a main body 3601,a display portion 3602, a frame 3603, external connection ports 3604, aremote control receiving portion 3605, an image receiving portion 3606,a battery 3607, an audio input portion 3608, operation keys 3609, andthe like. The light-emitting device of the present invention can be usedin the display portion 3602.

[0504]FIG. 13H is a mobile telephone, which is composed of a main body3701, a frame 3702, a display portion 3703, an audio input portion 3704,an audio output portion 3705, operation keys 3706, external connectionports 3707, an antenna 3708, and the like. The light-emitting device ofthe present invention can be used in the display portion 3703. Note thatwhite characters are displayed on a black background in the displayportion 3703, and thus, the power consumption of the mobile telephonecan be suppressed.

[0505] Note that, when a light emitting intensity of an organic lightemitting material is increased in future, it can be used for a fronttype or a rear type projector for magnifying and projecting outputtedlight including image information by a lens or the like.

[0506] Also, in the above electronic apparatuses, the number of caseswhere information distributed through an electronic communication linesuch as an Internet or a CATV (cable television) is displayed isincreased. In particular, a chance in which moving image information isdisplayed is increased. A response speed of the organic light emittingmaterial is very high. Thus, the light-emitting device is preferable formoving image display.

[0507] Also, with respect to the light-emitting device, power isconsumed in a portion that emits light. Thus, it is desirable thatinformation is displayed so as to minimize an area of a light-emittingportion. Accordingly, when the light-emitting device is used for adisplay portion of, a portable information terminal, particularly, amobile telephone or a sound reproducing device in which characterinformation is mainly displayed, it is desirable that the light-emittingdevice is driven so as to use a non-light emitting portion as abackground and produce character information in a light emittingportion.

[0508] As described above, an application area of the present inventionis extremely wide and the light-emitting device can be used forelectronic apparatuses in all fields. In addition, the light-emittingdevice having any structure described in Embodiments 1 to 7 may be usedfor the electronic apparatuses of this embodiment.

[0509] Embodiment 7

[0510] A phenomenon is used in the present invention as a method ofcorrecting the threshold value of transistors by making a short circuitbetween the gate and the drain of a transistor used in correction, andletting electric current flow between the source and the drain in thisdiode state, thus making the voltage between the source and the drainequal to the threshold value. It is also possible to apply thisphenomenon to driver circuits as well as to pixel portions as introducedby the present invention.

[0511] An electric current source circuit in a driver circuit foroutputting electric current to pixels and the like can be given as anexample. The electric current source circuit is a circuit in which apredetermined amount of electric current is output in accordance with aninput voltage signal. A voltage signal is input to a gate electrode ofan electric current source transistor within the electric current sourcecircuit, and an electric current corresponding to the voltage betweenthe gate and the source is output through the electric current sourcetransistor. That is, the method of the present invention for correctingthe threshold value is utilized in correcting the threshold value of theelectric current source transistor.

[0512] An example of utilizing the electric current source circuit isshown in FIG. 23A. Sampling pulses are output in order from a shiftregister, and the sampling pulses are each input to electric currentsource circuits 9001. Sampling of an image signal is performed inaccordance with the timing at which the sampling pulses are input to theelectric current source circuits 9001. Sampling operations are performedin a dot sequential manner in this case.

[0513] A simple operation timing is shown in FIG. 23B. A period forselecting a number i gate signal line is divided into a period forperforming sampling of an image signal, in which the sampling pulses areoutput from the shift register, and a retrace period. The thresholdvalue correction operations of the present invention are performed inthe retrace period. That is, operations for initializing the electricpotential of each portion, and operations for obtaining the transistorthreshold voltages are performed sequentially. In other words,operations for obtaining the threshold values can be performed persingle horizontal period.

[0514] The structure of a driver circuit for outputting electric currentto pixels, but which differs from the structure of FIGS. 23A and 23B, isshown in FIG. 24A. Differing from the case of FIGS. 23A and 23B, theelectric current source circuits 9001, which are controlled by one stageof sampling pulses, become two electric current source circuits 9001Aand 9001B, and both operations are selected by an electric currentsource control signal.

[0515] As shown in FIG. 24B, the electric current source control signalmay be made to change every single horizontal period, for example.Operation of the electric current source circuits 9001A and 9001B isthus performed so that one of the two circuits performs electric currentoutput to pixels and the like while the other circuit performs input ofthe image signal. These operations are switched every row. Samplingoperations are thus performed in a line sequential manner in this case.

[0516] A driver circuit having another different structure is shown inFIG. 25A. The image signal type may be either digital or analog in FIGS.23A and 23B, and FIGS. 24A and 24B, but a digital image signal is inputwith the structure of FIG. 25A. The input digital image signal is takenin by a first latch circuit in accordance with the output of samplingpulses, and is transferred to a second latch circuit after the input ofone row portion of the image signal is complete. This is later input tothe electric current source circuits 9001A and 9001B, and electriccurrent source circuits 9001C. The amounts of electric current valueoutput by the electric current source circuits 9001A to 9001C differ.For example, the ratio of the electric current values becomes 1:2:4.That is, n electric current source circuits may be disposed in parallel,the ratio of the electric current values of the circuits may be set as1:2:4: . . . :2^((n−1)), and the amount of electric current valuesoutput can be changed linearly by combining the electric currents outputfrom each of the electric current source circuits.

[0517] Operation timing is nearly the same as that shown in FIGS. 23Aand 23B. Threshold value correction is performed in the electric currentsource circuits 9001 within the retrace period during which samplingoperations are not performed, data stored in the latch circuits istransferred, and V-I conversion is performed in the electric currentsource circuits 9001 and electric current is output to pixels. Thesampling operations are performed in a line sequential manner, similarto the structure shown in FIGS. 24A and 24B.

[0518] The structure of another driver circuit for outputting electriccurrent to pixels and the like is shown in FIG. 26A. A digital imagesignal taken in by a latch circuit is transferred to a D/A convertercircuit by the input of a latching signal with this structure, and thedigital image signal is converted to an analog image signal. The analogimage signal is input to each of the electric current source circuits9001, which output electric current.

[0519] Further, other functions may also be given to this type of D/Aconverter circuit, such as gamma correction.

[0520] Threshold value correction and latch data transfer are performedwithin the retrace period as shown in FIG. 26B. V-I conversion of acertain row, and output of electric current to pixels and the like, areperformed during a period for performing sampling operations of the nextrow. The sampling operations are performed in a line sequential manner,similar to the structure shown in FIGS. 24A and 24B.

[0521] The present invention is not limited to the structures discussedabove, and it is possible to apply the threshold value correcting meansof the present invention to the case of performing V-I correction byusing an electric current source circuit. Further, a structure in whicha plurality of electric current source circuits are disposed inparallel, like the structure shown in FIGS. 24A and 24B, and used byswitching between the circuits may also be combined with otherstructures, such as those of FIGS. 25A and 25B, and those of FIGS. 26Aand 26B.

[0522] Dispersion in the threshold values of TFTs can be correctednormally by the present invention, without being influenced bydispersion and the like in the capacitance values of capacitor means,etc. In addition, although operations are often performed within onehorizontal period in the case of performing threshold value correctionin accordance with the structures shown in FIGS. 10A and 10B, and FIGS.11A to 11F, the present invention is based on a simple operatingprinciple. The operation timing is also simple, and therefore high speedcircuit operations become possible. In particular, it becomes possibleto display a high quality image using an image signal having a verylarge number of bits when performing display by a method in which adigital gray scale method and a time gray scale method are combined.

What is claimed is:
 1. A semiconductor device comprising: a rectifyingelement; capacitor means; and a switching element,  wherein: a firstelectrode of the rectifying element is electrically connected to a firstelectrode of the capacitor means and a first electrode of the switchingelement.
 2. A semiconductor device comprising: a first rectifyingelement having a first electrode; a second rectifying element having afirst electrode; and capacitor means,  wherein: a first electrode of thefirst rectifying element electrically connected to a first electrode ofthe capacitor means and a first electrode of the second rectifyingelement.
 3. A semiconductor device comprising: a rectifying element;capacitor means; and a switching element,  wherein: an electricpotential V₁ of a first electric power source is imparted to a firstelectrode of the rectifying element; a second electrode of therectifying element is electrically connected to a first electrode of thecapacitor means and a first electrode of the switching element; anelectric potential V₂ of a second electric power source is imparted to asecond electrode of the switching element; a signal having an electricpotential that is greater than or equal to an electric potential V₃ andless than or equal to (V₃+an electric potential V_(Data)), or greaterthan or equal to (V₃−V_(Data)) and less than or equal to V₃, is input toa second electrode of the capacitor means; and a signal having anelectric potential equal to any one of (V₁+|V_(th)|), V₂, and(V₁+|V_(th)|±V_(Data)) is obtained from the second electrode of therectifying element when a threshold voltage of the rectifying element istaken as V_(th).
 4. A semiconductor device comprising: a rectifyingelement; capacitor means; and a switching element,  wherein: an electricpotential V₁ of a first electric power source is imparted to a firstelectrode of the rectifying element; a second electrode of therectifying element is electrically connected to a first electrode of thecapacitor means and a first electrode of the switching element; anelectric potential V₂ of a second electric power source is imparted to asecond electrode of the switching element; a signal having an electricpotential that is greater than or equal to an electric potential V₃ andless than or equal to (V₃+an electric potential V_(Data)), or greaterthan or equal to (V₃−V_(Data)) and less than or equal to V₃, is input toa second electrode of the capacitor means; and a signal having anelectric potential equal to any one of (V₁−|V_(th)|), V₂, and(V₁−|V_(th)|+V_(Data)) is obtained from the second electrode of therectifying element when a threshold voltage of the rectifying element istaken as V_(th).
 5. A semiconductor device comprising: a firstrectifying element; a second rectifying element; and capacitor means, wherein: an electric potential V₁ of a first electric power source isimparted to a first electrode of the first rectifying element; a secondelectrode of the first rectifying element is electrically connected to afirst electrode of the capacitor means and a first electrode of thesecond rectifying element; a first signal having an electric potentialgreater than or equal to an electric potential V₂ and less than or equalto an electric potential V₂′ is input to a second electrode of thesecond rectifying element; a second signal having an electric potentialthat is greater than or equal to an electric potential V₃ and less thanor equal to (V₃+an electric potential V_(Data)), or greater than orequal to (V₃−V_(Data)) and less than or equal to V₃, is input to asecond electrode of the capacitor means; and a signal having an electricpotential equal to any one of (V₁−|V_(th)1|), (V₂+V_(th)2), and (V₁1−|V_(th)1|±V_(Data)) is obtained from the second electrode of the firstrectifying element when a threshold voltage of the first rectifyingelement is taken as V_(th)1 and a threshold voltage of the secondrectifying element is taken as V_(th)2.
 6. A semiconductor devicecomprising: a first rectifying element; a second rectifying element; andcapacitor means,  wherein: an electric potential V₁ of a first electricpower source is imparted to the first electrode of the first rectifyingelement; a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element; a first signal havinga voltage amplitude of an electric potential greater than or equal to anelectric potential V₂ and less than or equal to an electric potentialV₂′ is input to a second electrode of the second rectifying element; asecond signal having an electric potential that is greater than or equalto an electric potential V₃ and less than or equal to (V₃+an electricpotential V_(Data)), or greater than or equal to (V₃−V_(Data)) and lessthan or equal to V₃, is input to a second electrode of the capacitormeans; and a signal having an electric potential equal to any one of(V₁+V_(th)1), (V₂′−V_(th)2), and (V₁+V_(th)1+V_(Data)) is obtained fromthe second electrode of the first rectifying element when a thresholdvoltage of the first rectifying element is taken as V_(th)1 and athreshold voltage of the second rectifying element is taken as V_(th)2.7. A semiconductor device according to claim 3, wherein: the rectifyingelement is formed by using a transistor having a connection between itsgate and its drain; V₁<V₂ if the transistor having a connection betweenits gate and its drain is an n-channel transistor; and V₁>V₂ if thetransistor having a connection between its gate and its drain is ap-channel transistor.
 8. A semiconductor device according to claim 4,wherein: the rectifying element is formed by using a transistor having aconnection between its gate and its drain; V₁<V₂ if the transistorhaving a connection between its gate and its drain is an n-channeltransistor; and V₁>V₂ if the transistor having a connection between itsgate and its drain is a p-channel transistor.
 9. A semiconductor deviceaccording to claim 5, wherein: the first rectifying element is formed byusing a transistor having a connection between its gate and its drain;V₁<V₂ if the transistor having a connection between its gate and itsdrain is an n-channel transistor; and V₁>V₂ if the transistor having aconnection between its gate and its drain is a p-channel transistor. 10.A semiconductor device according to claim 6, wherein: the firstrectifying element is formed by using a transistor having a connectionbetween its gate and its drain; V₁<V₂ if the transistor having aconnection between its gate and its drain is an n-channel transistor;and V₁>V₂ if the transistor having a connection between its gate and itsdrain is a p-channel transistor.
 11. A semiconductor device according toclaim 1, further comprising a transistor, wherein a gate electrode ofthe transistor is electrically connected to the first electrode of thecapacitor means.
 12. A semiconductor device according to claim 2,further comprising a transistor, wherein a gate electrode of thetransistor is electrically connected to the first electrode of thecapacitor means.
 13. A semiconductor device according to claim 3,further comprising a transistor, wherein a gate electrode of thetransistor is electrically connected to the first electrode of thecapacitor means.
 14. A semiconductor device according to claim 4,further comprising a transistor, wherein a gate electrode of thetransistor is electrically connected to the first electrode of thecapacitor means.
 15. A semiconductor device according to claim 5,further comprising a transistor, wherein a gate electrode of thetransistor is electrically connected to the first electrode of thecapacitor means.
 16. A semiconductor device according to claim 6,further comprising a transistor, wherein a gate electrode of thetransistor is electrically connected to the first electrode of thecapacitor means.
 17. A semiconductor device comprising a plurality ofpixels, each pixel including: a source signal line; a first gate signalline; a second gate signal line; a reset electric power source line; anelectric current supply line; a first transistor; a second transistor; athird transistor; a fourth transistor; capacitor means; and a lightemitting element,  wherein: a gate electrode of the first transistor iselectrically connected to the first gate signal line; a first electrodeof the first transistor is electrically connected to the source signalline; a second electrode of the first transistor is electricallyconnected to a first electrode of the capacitor means; a secondelectrode of the capacitor means is electrically connected to a gateelectrode of the second transistor, a first electrode of the secondtransistor, and a gate electrode of the third transistor; a secondelectrode of the second transistor is electrically connected to thereset electric power source line; a first electrode of the thirdtransistor is electrically connected to the electric current supplyline; a second electrode of the third transistor is electricallyconnected to a first electrode of the light emitting element; a gateelectrode of the fourth transistor is electrically connected to thesecond gate signal line; a first electrode of the fourth transistor iselectrically connected to the source signal line or the second electrodeof the first transistor; and a second electrode of the fourth transistoris electrically connected to the gate electrode of the secondtransistor, the first electrode of the second transistor, and the gateelectrode of the third transistor.
 18. A semiconductor device comprisinga plurality of pixels, each pixel including: a source signal line; afirst gate signal line; a second gate signal line; a reset electricpower source line; an electric current supply line; a first transistor;a second transistor; a third transistor; capacitor means; a diode; and alight emitting element,  wherein: a gate electrode of the firsttransistor is electrically connected to the first gate signal line; afirst electrode of the first transistor is electrically connected to thesource signal line; a second electrode of the first transistor iselectrically connected to a first electrode of the capacitor means; asecond electrode of the capacitor means is electrically connected to agate electrode of the second transistor, a first electrode of the secondtransistor, and a gate electrode of the third transistor; a secondelectrode of the second transistor is electrically connected to thereset electric power source line; a first electrode of the thirdtransistor is electrically connected to the electric current supplyline; a second electrode of the third transistor is electricallyconnected to a first electrode of the light emitting element; a firstelectrode of the diode is electrically connected to the gate electrodeof the second transistor, the first electrode of the second transistor,and the gate electrode of the third transistor; and a second electrodeof the diode is electrically connected to the second gate signal line.19. A semiconductor device comprising a plurality of pixels, each pixelincluding: a source signal line; a first gate signal line; a second gatesignal line; a reset electric power source line; an electric currentsupply line; a first transistor; a second transistor; a thirdtransistor; a first capacitor means; a second capacitor means; and alight emitting element,  wherein: a gate electrode of the firsttransistor is electrically connected to the first gate signal line; afirst electrode of the first transistor is electrically connected to thesource signal line; a second electrode of the first transistor iselectrically connected to a first electrode of the first capacitormeans; a second electrode of the first capacitor means is electricallyconnected to a gate electrode of the second transistor, a firstelectrode of the second transistor, and a gate electrode of the thirdtransistor; a second electrode of the second transistor is electricallyconnected to the reset electric power source line; a first electrode ofthe third transistor is electrically connected to the electric currentsupply line; a second electrode of the third transistor is electricallyconnected to a light emitting element; a first electrode of the secondcapacitor means is electrically connected to the gate electrode of thesecond transistor, the first electrode of the second transistor, and thegate electrode of the third transistor; and a second electrode of thesecond capacitor means is electrically connected to the second gatesignal line.
 20. A semiconductor device comprising a plurality ofpixels, each pixel including: a source signal line; a first gate signalline; a second gate signal line; a third gate signal line; a resetelectric power source line; an electric current supply line; a firsttransistor; a second transistor; a third transistor; a fourthtransistor; a fifth transistor; a first capacitor means; a secondcapacitor means; and a light emitting element,  wherein: a gateelectrode of the first transistor is electrically connected to the firstgate signal line; a first electrode of the first transistor iselectrically connected to the source signal line; a second electrode ofthe first transistor is electrically connected to a first electrode ofthe first capacitor means; a second electrode of the first capacitormeans is electrically connected to a gate electrode of the secondtransistor, a first electrode of the second transistor, and a gateelectrode of the third transistor; a second electrode of the secondtransistor is electrically connected to the reset electric power sourceline; a first electrode of the third transistor is electricallyconnected to the electric current supply line; a second electrode of thethird transistor is electrically connected to a light emitting elements;a gate electrode of the fourth transistor is electrically connected tothe second gate signal line; a first electrode of the fourth transistoris electrically connected to the source signal line or the secondelectrode of the first transistor; a second electrode of the fourthtransistor is electrically connected to the gate electrode of the secondtransistor, the first electrode of the second transistor, and the gateelectrode of the third transistor; a first electrode of the secondcapacitor means is electrically connected to the second electrode of thefirst transistor; a second electrode of the second capacitor means iselectrically connected to the second electrode of the third transistor;a gate electrode of the fifth transistor is electrically connected tothe third gate signal line; a first electrode of the fifth transistor iselectrically connected to the second electrode of the third transistor;and a second electrode of the fifth transistor is connected to anelectric power source electric potential that is equal to or lower thanan electric potential of a second electrode of the light emittingelement.
 21. A semiconductor device according to claim 17, furthercomprising: an erasure gate signal line; and an erasure transistor, wherein: a gate electrode of the erasure transistor is electricallyconnected to the erasure gate signal line; a first electrode of theerasure transistor is electrically connected to the electric currentsupply line; and the second electrode of the erasure transistor iselectrically connected to the gate electrode of the third transistor.22. A semiconductor device according to claim 18, further comprising: anerasure gate signal line; and an erasure transistor,  wherein: a gateelectrode of the erasure transistor is electrically connected to theerasure gate signal line; a first electrode of the erasure transistor iselectrically connected to the electric current supply line; and thesecond electrode of the erasure transistor is electrically connected tothe gate electrode of the third transistor.
 23. A semiconductor deviceaccording to claim 19, further comprising: an erasure gate signal line;and an erasure transistor,  wherein: a gate electrode of the erasuretransistor is electrically connected to the erasure gate signal line; afirst electrode of the erasure transistor is electrically connected tothe electric current supply line; and the second electrode of theerasure transistor is electrically connected to the gate electrode ofthe third transistor.
 24. A semiconductor device according to claim 20,further comprising: an erasure gate signal line; and an erasuretransistor,  wherein: a gate electrode of the erasure transistor iselectrically connected to the erasure gate signal line; a firstelectrode of the erasure transistor is electrically connected to theelectric current supply line; and the second electrode of the erasuretransistor is electrically connected to the gate electrode of the thirdtransistor.
 25. A semiconductor device according to claim 17, furthercomprising: an erasure gate signal line; and an erasure transistor, wherein: a gate electrode of the erasure transistor is electricallyconnected to the erasure gate signal line; a first electrode of theerasure transistor is electrically connected to the electric currentsupply line; and a second electrode of the erasure transistor iselectrically connected to the second electrode of the first transistor.26. A semiconductor device according to claim 18, further comprising: anerasure gate signal line; and an erasure transistor,  wherein: a gateelectrode of the erasure transistor is electrically connected to theerasure gate signal line; a first electrode of the erasure transistor iselectrically connected to the electric current supply line; and a secondelectrode of the erasure transistor is electrically connected to thesecond electrode of the first transistor.
 27. A semiconductor deviceaccording to claim 19, further comprising: an erasure gate signal line;and an erasure transistor,  wherein: a gate electrode of the erasuretransistor is electrically connected to the erasure gate signal line; afirst electrode of the erasure transistor is electrically connected tothe electric current supply line; and a second electrode of the erasuretransistor is electrically connected to the second electrode of thefirst transistor.
 28. A semiconductor device according to claim 20,further comprising: an erasure gate signal line; and an erasuretransistor,  wherein: a gate electrode of the erasure transistor iselectrically connected to the erasure gate signal line; a firstelectrode of the erasure transistor is electrically connected to theelectric current supply line; and a second electrode of the erasuretransistor is electrically connected to the second electrode of thefirst transistor.
 29. A semiconductor device according to claim 17,further comprising: an erasure gate signal line; and an erasuretransistor,  wherein: the erasure transistor is formed between theelectric current supply line and the first electrode of the thirdtransistor, or between the second electrode of the third transistor andthe first electrode of the light emitting element; and a gate electrodeof the erasure transistor is electrically connected to the erasure gatesignal line.
 30. A semiconductor device according to claim 18, furthercomprising: an erasure gate signal line; and an erasure transistor, wherein: the erasure transistor is formed between the electric currentsupply line and the first electrode of the third transistor, or betweenthe second electrode of the third transistor and the first electrode ofthe light emitting element; and a gate electrode of the erasuretransistor is electrically connected to the erasure gate signal line.31. A semiconductor device according to claim 19, further comprising: anerasure gate signal line; and an erasure transistor,  wherein: theerasure transistor is formed between the electric current supply lineand the first electrode of the third transistor, or between the secondelectrode of the third transistor and the first electrode of the lightemitting element; and a gate electrode of the erasure transistor iselectrically connected to the erasure gate signal line.
 32. Asemiconductor device according to claim 20, further comprising: anerasure gate signal line; and an erasure transistor,  wherein: theerasure transistor is formed between the electric current supply lineand the first electrode of the third transistor, or between the secondelectrode of the third transistor and the first electrode of the lightemitting element; and a gate electrode of the erasure transistor iselectrically connected to the erasure gate signal line.
 33. Asemiconductor device according to claim 17, wherein the secondtransistor and the third transistor have the same polarity.
 34. Asemiconductor device according to claim 18, wherein the secondtransistor and the third transistor have the same polarity.
 35. Asemiconductor device according to claim 19, wherein the secondtransistor and the third transistor have the same polarity.
 36. Asemiconductor device according to claim 20, wherein the secondtransistor and the third transistor have the same polarity.
 37. A methodof driving a semiconductor device, the semiconductor device comprising:a rectifying element; capacitor means; and a switching element, wherein: an electric potential V₁ of a first electric power source isimparted to a first electrode of the rectifying element; a secondelectrode of the rectifying element is electrically connected to a firstelectrode of the capacitor means and a first electrode of the switchingelement; and an electric potential V₂ of a second electric power sourceis imparted to a second electrode of the switching element; the methodof driving the semiconductor device comprising: when a threshold voltageof the rectifying element is taken as V_(th), a first step of making theswitching element conductive and setting the electric potential of asecond electrode of the rectifying element to V₂; and a second step ofmaking the switching element non-conductive, making the voltage betweenboth electrodes of the rectifying element converge to the thresholdvoltage V_(th), and setting the electric potential of the secondelectrode of the rectifying element to (V₁+V_(th)).
 38. A method ofdriving a semiconductor device, the semiconductor device comprising: arectifying element; capacitor means; and a switching element,  wherein:an electric potential V₁ of a first electric power source is imparted toa first electrode of the rectifying element; a second electrode of therectifying element is electrically connected to the first electrode ofthe capacitor means and a first electrode of the switching element; anelectric potential V₂ of a second electric power source is imparted to asecond electrode of the switching element; and a signal having anelectric potential that is greater than or equal to an electricpotential V₃ and less than or equal to (V₃+an electric potentialV_(Data)), or greater than or equal to (V₃−V_(Data)) and less than orequal to V₃, is input to a second electrode of the capacitor means; themethod of driving the semiconductor device comprising: when a thresholdvoltage of the rectifying element is taken as V_(th), a first step ofmaking the switching element conductive and setting the electricpotential of a second electrode of the rectifying element to V₂; asecond step of making the switching element non-conductive, making thevoltage between both electrodes of the rectifying element converge tothe threshold voltage V_(th), and setting the electric potential of thesecond electrode of the rectifying element to (V₁+V_(th)); and a thirdstep of changing the electric potential of the second electrode of thecapacitor means by V_(Data), and setting the electric potential of thesecond electrode of the rectifying element to (V₁+V_(th)±V_(Data)). 39.A method of driving a semiconductor device, the semiconductor devicecomprising: a rectifying element; capacitor means; and a switchingelement,  wherein: an electric potential V₁ of a first electric powersource is imparted to a first electrode of the rectifying element; asecond electrode of the rectifying element is electrically connected toa first electrode of the capacitor means and a first electrode of theswitching element; and an electric potential V₂ of a second electricpower source is imparted to a second electrode of the switching element;the method of driving the semiconductor device comprising: when athreshold voltage of the rectifying element is taken as V_(th), a firststep of making the switching element conductive and setting the electricpotential of the second electrode of the rectifying element to V₂; and asecond step of making the switching element non-conductive, making thevoltage between both electrodes of the rectifying element converge tothe threshold voltage V_(th), and setting the electric potential of thesecond electrode of the rectifying element to (V₁−|V_(th)|).
 40. Amethod of driving a semiconductor device, the semiconductor devicecomprising: a rectifying element; capacitor means; and a switchingelement,  wherein: an electric potential V₁ of a first electric powersource is imparted to a first electrode of the rectifying element; asecond electrode of the rectifying element is electrically connected toa first electrode of the capacitor means and a first electrode of theswitching element; an electric potential V₂ of a second electric powersource is imparted to a second electrode of the switching element; and asignal having an electric potential that is greater than or equal to anelectric potential V₃ and less than or equal to (V₃+an electricpotential V_(Data)), or greater than or equal to (V₃−V_(Data)) and lessthan or equal to V₃, is input to a second electrode of the capacitormeans; the method of driving the semiconductor device comprising: when athreshold voltage of the rectifying element is taken as V_(th), a firststep of making the switching element conductive and setting the electricpotential of the second electrode of the rectifying element to V₂; asecond step of making the switching element non-conductive, making thevoltage between both electrodes of the rectifying element converge tothe threshold voltage V_(th), and setting the electric potential of thesecond electrode of the rectifying element to (V₁−|V_(th)|); and a thirdstep of changing the electric potential of the second electrode of thecapacitor means by V_(Data), and setting the electric potential of thesecond electrode of the rectifying element to (V₁−|V_(th)|±V_(Data)).41. A method of driving a semiconductor device according to claim 38,wherein: the semiconductor device further comprises a transistor; and agate electrode of the transistor is electrically connected to the secondelectrode of the rectifying element.
 42. A method of driving asemiconductor device according to claim 40, wherein: the semiconductordevice further comprises a transistor; and a gate electrode of thetransistor is electrically connected to the second electrode of therectifying element.
 43. A method of driving a semiconductor device, thesemiconductor device comprising: a first rectifying element having afirst electrode and a second electrode; a second rectifying elementhaving a first electrode and a second electrode; and capacitor means, wherein: an electric potential V₁ of a first electric power source isimparted to a first electrode of the first rectifying element; a secondelectrode of the first rectifying element is electrically connected to afirst electrode of the capacitor means and a first electrode of thesecond rectifying element; and a first signal having an electricpotential greater than or equal to an electric potential V₂ and lessthan or equal to an electric potential V₂′ is input to a secondelectrode of the second rectifying element; the method of driving thesemiconductor device comprising: when a threshold voltage of the firstrectifying element is taken as V_(th)1 and a threshold voltage of thesecond rectifying element is taken as V_(th)2, a first step of settingthe electric potential of a second electrode of the second capacitormeans to V₂, and setting the electric potential of the second electrodeof the first rectifying element to (V₂+V_(th)2); and a second step ofsetting the electric potential of a second electrode of the secondcapacitor means to V₂′, making the voltage between both electrodes ofthe first rectifying element converge to the threshold voltage V_(th)1,and setting the electric potential of the second electrode of the firstrectifying element to (V₁−|V_(th)1|).
 44. A method of driving asemiconductor device, the semiconductor device comprising: a firstrectifying element; a second rectifying element; and capacitor means, wherein: an electric potential V₁ of a first electric power source isimparted to a first electrode of the first rectifying element; a secondelectrode of the first rectifying element is electrically connected to afirst electrode of the capacitor means and a first electrode of thesecond rectifying element; a first signal having an electric potentialgreater than or equal to an electric potential V₂ and less than or equalto an electric potential V₂′ is input to a second electrode of thesecond rectifying element; and a second signal having an electricpotential that is greater than or equal to an electric potential V₃ andless than or equal to (V₃+an electric potential V_(Data)), or greaterthan or equal to (V₃−V_(Data)) and less than or equal to V₃, is input toa second electrode of the capacitor means; the method of driving thesemiconductor device comprising: when a threshold voltage of the firstrectifying element is taken as V_(th)1 and a threshold voltage of thesecond rectifying element is taken as V_(th)2, a first step of settingthe electric potential of the second electrode of the second capacitormeans to V₂, and setting the electric potential of the second electrodeof the first rectifying element to (V₂+V_(th)2); a second step ofsetting the electric potential of a second electrode of the secondcapacitor means to V₂′, making the voltage between both electrodes ofthe first rectifying element converge to the threshold voltage V_(th)1,and setting the electric potential of the second electrode of the firstrectifying element to (V₁−|V_(th)1|); and a third step of changing theelectric potential of the second electrode of the capacitor means byV_(Data), and setting the electric potential of the second electrode ofthe first rectifying element to (V₁−|V_(th)1|±V_(Data)).
 45. A method ofdriving a semiconductor device, the semiconductor device comprising: afirst rectifying element; a second rectifying element; and capacitormeans;  wherein: an electric potential V₁ of a first electric powersource is imparted to the first electrode of the first rectifyingelement; a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element; and a first signalhaving an electric potential greater than or equal to an electricpotential V₂ and less than or equal to an electric potential V₂′ isinput to a the second electrode of the second rectifying element; themethod of driving the semiconductor device comprising: when a thresholdvoltage of the first rectifying element is taken as V_(th)1 and athreshold voltage of the second rectifying element is taken as V_(th)2,a first step of setting the electric potential of a second electrode ofthe second capacitor means to V₂,′ and setting the electric potential ofthe second electrode of the first rectifying element to (V₂′−|V_(th)2|);and a second step of setting the electric potential of a secondelectrode of the second capacitor means to V₂, making the voltagebetween both electrodes of the first rectifying element converge to thethreshold voltage V_(th)1, and setting the electric potential of thesecond electrode of the first rectifying element to (V₁+V_(th)1).
 46. Amethod of driving a semiconductor device, the semiconductor devicecomprising: a first rectifying element; a second rectifying element; andcapacitor means,  wherein: an electric potential V₁ of a first electricpower source is imparted to a first electrode of the first rectifyingelement; a second electrode of the first rectifying element iselectrically connected to a first electrode of the capacitor means and afirst electrode of the second rectifying element; a first signal havingan electric potential greater than or equal to an electric potential V₂and less than or equal to an electric potential V₂′ is input to a secondelectrode of the second rectifying element; and a second signal havingan electric potential that is greater than or equal to an electricpotential V₃ and less than or equal to (V₃+an electric potentialV_(Data)), or greater than or equal to (V₃−V_(Data)) and less than orequal to V₃, is input to a second electrode of the capacitor means; themethod of driving the semiconductor device comprising: when a thresholdvoltage of the first rectifying element is taken as V_(th)1 and athreshold voltage of the second rectifying element is taken as V_(th)2,a first step of setting the electric potential of the second electrodeof the second capacitor means to V₂′, and setting the electric potentialof the second electrode of the first rectifying element to(V₂′−|V_(th)2|); a second step of setting the electric potential of asecond electrode of the second capacitor means to V₂, making the voltagebetween both electrodes of the first rectifying element converge to thethreshold voltage V_(th)1, and setting the electric potential of thesecond electrode of the first rectifying element to (V₁+V_(th)1); and athird step of changing the electric potential of the second electrode ofthe capacitor means by V_(Data), and setting the electric potential ofthe second electrode of the first rectifying element to(V₁+V_(th)1±V_(Data)).
 47. A method of driving a semiconductor deviceaccording to claim 44, wherein: the semiconductor device furthercomprises a transistor; and a gate electrode of the transistor iselectrically connected to the second electrode of the first rectifyingelement.
 48. A method of driving a semiconductor device according toclaim 46, wherein: the semiconductor device further comprises atransistor; and a gate electrode of the transistor is electricallyconnected to the second electrode of the first rectifying element.
 49. Amethod of driving a semiconductor device according to claim 37, wherein:the rectifying element is formed by using a transistor having aconnection between its gate and its drain; V₁<V₂ if the transistorhaving a connection between its gate and its drain is an n-channeltransistor; and V₁>V₂ if the transistor having a connection between itsgate and its drain is a p-channel transistor.
 50. A method of driving asemiconductor device according to claim 38, wherein: the rectifyingelement is formed by using a transistor having a connection between itsgate and its drain; V₁<V₂ if the transistor having a connection betweenits gate and its drain is an n-channel transistor; and V₁>V₂ if thetransistor having a connection between its gate and its drain is ap-channel transistor.
 51. A method of driving a semiconductor deviceaccording to claim 39, wherein: the rectifying element is formed byusing a transistor having a connection between its gate and its drain;V₁<V₂ if the transistor having a connection between its gate and itsdrain is an n-channel transistor; and V₁>V₂ if the transistor having aconnection between its gate and its drain is a p-channel transistor. 52.A method of driving a semiconductor device according to claim 40,wherein: the rectifying element is formed by using a transistor having aconnection between its gate and its drain; V₁<V₂ if the transistorhaving a connection between its gate and its drain is an n-channeltransistor; and V₁>V₂ if the transistor having a connection between itsgate and its drain is a p-channel transistor.
 53. A method of driving asemiconductor device according to claim 43, wherein: the firstrectifying element is formed by using a transistor having a connectionbetween its gate and its drain; V₁<V₂ if the transistor having aconnection between its gate and its drain is an n-channel transistor;and V₁>V₂ if the transistor having a connection between its gate and itsdrain is a p-channel transistor.
 54. A method of driving a semiconductordevice according to claim 44, wherein: the first rectifying element isformed by using a transistor having a connection between its gate andits drain; V₁<V₂ if the transistor having a connection between its gateand its drain is an n-channel transistor; and V₁>V₂ if the transistorhaving a connection between its gate and its drain is a p-channeltransistor.
 55. A method of driving a semiconductor device according toclaim 45, wherein: the first rectifying element is formed by using atransistor having a connection between its gate and its drain; V₁<V₂ ifthe transistor having a connection between its gate and its drain is ann-channel transistor; and V₁>V₂ if the transistor having a connectionbetween its gate and its drain is a p-channel transistor.
 56. A methodof driving a semiconductor device according to claim 46, wherein: thefirst rectifying element is formed by using a transistor having aconnection between its gate and its drain; V₁<V₂ if the transistorhaving a connection between its gate and its drain is an n-channeltransistor; and V₁>V₂ if the transistor having a connection between itsgate and its drain is a p-channel transistor.
 57. A semiconductor deviceaccording to claim 1, wherein the semiconductor device is applied in anelectronic apparatus selected from the group consisting of a videocamera, a digital camera, a goggle type display, a laptop computer, agame machine, a portable information terminal, a DVD player and a mobiletelephone.
 58. A semiconductor device according to claim 2, wherein thesemiconductor device is applied in an electronic apparatus selected fromthe group consisting of a video camera, a digital camera, a goggle typedisplay, a laptop computer, a game machine, a portable informationterminal, a DVD player and a mobile telephone.
 59. A semiconductordevice according to claim 3, wherein the semiconductor device is appliedin an electronic apparatus selected from the group consisting of a videocamera, a digital camera, a goggle type display, a laptop computer, agame machine, a portable information terminal, a DVD player and a mobiletelephone.
 60. A semiconductor device according to claim 4, wherein thesemiconductor device is applied in an electronic apparatus selected fromthe group consisting of a video camera, a digital camera, a goggle typedisplay, a laptop computer, a game machine, a portable informationterminal, a DVD player and a mobile telephone.
 61. A semiconductordevice according to claim 5, wherein the semiconductor device is appliedin an electronic apparatus selected from the group consisting of a videocamera, a digital camera, a goggle type display, a laptop computer, agame machine, a portable information terminal, a DVD player and a mobiletelephone.
 62. A semiconductor device according to claim 6, wherein thesemiconductor device is applied in an electronic apparatus selected fromthe group consisting of a video camera, a digital camera, a goggle typedisplay, a laptop computer, a game machine, a portable informationterminal, a DVD player and a mobile telephone.
 63. A semiconductordevice according to claim 17, wherein the semiconductor device isapplied in an electronic apparatus selected from the group consisting ofa video camera, a digital camera, a goggle type display, a laptopcomputer, a game machine, a portable information terminal, a DVD playerand a mobile telephone.
 64. A semiconductor device according to claim18, wherein the semiconductor device is applied in an electronicapparatus selected from the group consisting of a video camera, adigital camera, a goggle type display, a laptop computer, a gamemachine, a portable information terminal, a DVD player and a mobiletelephone.
 65. A semiconductor device according to claim 19, wherein thesemiconductor device is applied in an electronic apparatus selected fromthe group consisting of a video camera, a digital camera, a goggle typedisplay, a laptop computer, a game machine, a portable informationterminal, a DVD player and a mobile telephone.
 66. A semiconductordevice according to claim 20, wherein the semiconductor device isapplied in an electronic apparatus selected from the group consisting ofa video camera, a digital camera, a goggle type display, a laptopcomputer, a game machine, a portable information terminal, a DVD playerand a mobile telephone.